The Fairlight explained
Contents
1. feature is that loop parameters are saved with the voice information as well as any oa Linked control file so that the sound is _ Playable even though no performance controls are required The actual loop points are displayed graphically on Page 4 as shown in Figure 4 where the horizontal axis represents the segment number and therefore time The loop is indicated by the row of highlighted boxes under the Harmonic Profiles graph and since the voice shown was sampled there are none of these present This Page offers a convenient method of selecting looping points using the light pen Start Seg is a powerful expression control It allows the starting segment of the voice to be chosen according to a control value as a new key is played To explain suppose we had sampled the classic synthesiser filter sweep and play ing the keyboard resulted in a fruity decay Using a control fader to set the start segment would then enable us to play the synth sound from different parts s fof the filter sweep As the control was t moved from segment 1 to 128 the sound would begin with plenty of filter sizzle at low control values but become shorter oo and more mellow as we started the sound s further down the sweep by increasing the Start Segment number This tech nique can also be used io control the amount of breath on sampled wind sounds or the amount of bowing on stringed instruments Ne2. F SUTCH ON OFF ZERO KEYVEL INDER t OMMANI PENE PAGE 4 READY A ML ALLL LT eaaa a Oe Nee nee oer oa tae a seta WS ace CLEAR DELETE RESET ZERO COMPUTE INTERP ON i E 95 SKAR ngre COMPUTER MUSICIAN THE FAIRLIGHT JIC IP I A ILIN ID Sampling may be the CMI s most talked about feature but as this article shows defining sounds using harmonic information can be just as dramatic method of actually creating sounds with the Fairlight sampling This aspect of sound formation is probably the single most important feature of the CMI and was certainly the focus of public attention when the machine was an nounced However the ability to specify sound by means of harmonic information can not only result in some very interesting sounds it s also rather useful in an educational environment Two display Pages 4 and 5 allow the construction of waveforms by harmonic data They deal with exactly the same information but present it to the musician in different ways First of all though let s clear up a little mystery that s been evading us for some months the Mode switch Actually this is very simple and is therefore something of an anti climax When a voice operates in Mode 1 only the first 32 segments of waveform RAM 4k bytes are used to represent the sound An unlooped Mode 1 sound will stop at the 32nd segment even though another 96 segments of
3. The Slur switch is useful for glissando Meee CLM ty chill i TERIN MBER Wai Ess fy A portamento effects as it causes Channel cards allocated to a voice to sustain indefinitely in a loop that may be jactive until a new note is played New 4 notes are started at the beginning of the loop without playing any of the preceding segments Sustain determines the be haviour of the voice once the key is released Normally a voice fades out either playing its loop or until it hits the end of the segments but when Sustain is on Damping is ignored and the voice 3 loops for the duration of key depression upon key release the voice continues to 5 play its remaining segments with no f decay of amplitude Looping Choosing the correct looping point of a voice waveform can make or break a good sound on the Fairlight Nasty glitches can occur if an inappropriate sample rate is chosen or if the section to be looped spans a natural change of amplitude Imagine trying to loop a percussive sound such as a drum The three loop controls on Page 7 provide a quick way of finding the best loop and a typical setting might be as shown in Figure 3 Here Control 1 is used to define start point of the loop while Control 2 sets the length Switch 1 freezes the effect of Control 1 and Control 2 when off preventing acci dental movement of the looping points once these have been decided A useful
4. Sample Rate Although sampling itself is very simple and impressive results can be obtained very quickly it s well worth the trouble spending some time adjusting the Sample Rate to a value that suits the pitch of the input signal The sound as piayed on the keyboard will oniy be in tune if one cycle of the resulting sampled waveform fits exactly into one segment of waveform RAM Remember one segment is 128 bytes This is achieved when the Sample Rate equals the frequency of the input signal multiplied by 128 ie 128 samples per cycle Since we can adjust the tuning of the voices on Page 3 an out of tune sample is not in itself a problem However there is one more important aspect of the CMI that obliges us to pay attention to the correct sample rate The number of original samples taken is fixed and equals the length of the waveform RAM ie 16384 The faster these samples are taken the shorter the duration of the sound becomes although the fidelity increases This 86 results in a short sound when the sample is played on the keyboard and this becomes shorter as we ascend the octaves To over come this the Fairlight allows sections of the waveform RAM to be read out repeatedly or looped as the key is held down thus sustain ing the sound The smallest section of RAM than can be looped is known as a Segmeit Here lies the crux of choosing a suitable Sample Rate If we attempt to loop a Segment or group of segments
5. minimum MSB 1 1111 1111 Figure 5 Non linear logarithmic conversion DISPLAY FORMAT 3B Figure 6 maximum Amplitude maximum Voice Waveform SAMPLE RATE FILTER LOW FILTER HIGH COMPRESSOR SAMPLE DISPLAY 011 1111 WDE 1 SYNTOM SOUND SAMPLING 14080 HZ SAMPLE LEVEL 1 TRIGGER LEVEL TRIGGER DELAY 8 OFF T Amplitude SAMPLE RATE FILTER LOW FILTER HIGH Voice Waveform COMPRESSOR Triangle SAMPLE DISPLAY Figure 9 VOICE 1 PACE 2 PEAD tt Hus SYNTOM SOUND SAMPLING 14888 HZ SAMPLE LEVEL TRIGGER LEVEL 8 TRIGGER DELAY OFF VD TH MIXCOM MODE 4 Figure 10 Linearity Now seems as good a time as any to explain something we ve mentioned many times in the past but haven t really discussed in any detail namely the difference between linear and non linear voice data As you may remember a E amp MM MAY 1985 waveform is stored in 16K of RAM in which each byte has a binary value that corresponds directly to the amplitude of the waveform at that point A byte consists of eight bits and considering all the possible combinations of these res ults in the amplitude of the sound at any point being limited to one of 256 levels The term linear refers to the relationship between the actual amplitude and the value of the binary number used to represent it If all this sounds a bit on the technical side and it ought to have
6. 1 and forces it to produce a stream of pulses ata frequency of 128 times the sample rate shown on Page 8 This is supplied to the ADC which resides on the Master card and once the sampling process is finished the CPU restores Channel 1 to its original task Trigger Level is the amplitude threshold at which the sampling process is triggered to begin When the Sample command is given the system waits until this level is reached before proceeding Once the threshold has been exceeded it s possible to delay the conversion by using the Trigger Delay which has a range of 0 65533 milliseconds This can be especially useful when sampling from tape shortly before the signal to be sampled and used instead of the signal itself to trigger the sampling process Trigger Delay can then be used to define the precise point at which sampling will actually begin This is extremely useful for sounds with a gentle attack such as slow strings Lastly the Compressor is a software switch which controls a hardware option Basically this turns the conversion process into a non linear system thus enhancing the dynamic range The electronics use the same type of circuitry as that in many analogue companding systems However very few Fairlights are fitted with this option as it can have a strange effect on the commands on Page 6 Well that about wraps it up for Page 8 There isn t room this month for a discussion on Page 7 so we ll have to leave
7. DISPLAY DISK CONTROL LORD QUERY CMI GUM meL STE CBELLOOO PAGE 2 READY WITH ALL TYFES OF FILESS MULTI CANCEL repre coe BASSCT TANN size 24 STRMID GANGSA CE signal Figure 3 Fairlight channel cards with specimen waveforms illustrated Computer motherboard Address bus Data p bus Control Control bus circuitry Waveform RAM oulput AUGUST 1984 E amp MM UMS and types aay SPACE on disk GTi number E instrument or voice files instrument files voice files sequence files command command protection on master keyboard shortcuts For HELP touch any BOX with LIGHTPEN or type niset gt d where n sheet no For HELP with HELP PAGES touch or type Hi lt return gt NSOnnn fh A WOW WA wo wo Figure 4 TO TRANSFER FILES TO ANOTHER DISK TYPE T file lt return gt LIGHTPEN lt select files gt or lt TRANSFER gt T file file filel ete lt return gt where file FITLENRAME SF or 8 or or amp same as DELETE see above EXAMPLES T CHORUS IN lt return gt T 4 18 ABLE VC 2S lt return gt Files will be copied FROM disk in RH drive DISK A TO another disk in LH drive DISK B Give TRANSFER command with system disk in LH drive and DISK A in RH drive When the message PLACE FILE DISK IN LH DRIVE appears place DISK B in LH drive When the transfer is completed a final message will
8. Enter Page 4 Figure 1 is a typical Page 4 display and shows that it s one of the two Fairlight display Pages to be almost exclusively lightpen driven The large dark area is in fact a reverse video image and pointing the lightpen in this region results in an arrow cursor appearing on the screen at the current lightpen position For those unfamiliar with the term the lightpen is now a fairly common computer add on mainly because of its simplicity of opera tion Contained within every lightpen is a fast photoelectric diode or transistor which produces a voltage pulse as the TV line passes beneath it Usually the pulse iS squared up and passed to the video controller chip which stores the TV line number and position along the line in a couple of registers This information can then be used by the programmer to initiate predefined events such as plotting a point or executing a command The Fairlight system is no different except that the video controller is con structed from discrete logic chips and resides on a single eight inch board within the CPU In addition to latching the TV co ordinates when the lightpen is used it generates an interrupt to the processors to execute the selected task At first glance the graph area in Figure 1 looks a bit confusing but it s really quite straightforward the vertical axis repre sents amplitude while the horizontal shows time and hence the segment number 86 J ust when you though
9. PAN VC which can be s en in Figure 11 The breath chiff is clearly visible at the beginning of the sound but unfortu nately the sampling started a fraction too soon and the waveform has a few initial segments of low level rubbish nothing to do with Electronic Soundmaker you understand The cure is to rotate the voice left to bring the start of the sound proper coincident with the start of the RAM The next step is to flick to Voice 1 in Register A and ZERO it Using a new command TRANSFER the first few segments from PAN VC can be copied to the blank voice currently selected Stab bing the keyboard at this juncture reveals that all is well so the next thing to do is to ive Tust BOUGHT THIS NEW MEGA AUTO COMPOSER SOFTWARE eel COST ME 5007 THINK THEY SAW YOU COMING MATE IT CONTAINS ALLOF THE TECHNIQUES AND STYLES OF THE WORLDS GREAT EST COMPOSERS CAN TURN THE MOST BORING AND MEDIOCRE SONG INTO AN UNFORGETTABLE CLASSIC If SAYS HERE COMPUTER MUSICIAN work on the body of the sound itself Before any sound can really make the grade as far as aesthetics are concerned it must have plenty of timbral and amplitude movement within it A good way of producing harmonically rich waveforms is to use Page 5 and create a few segments spread across those un used by the chiff Figure 12 gives the general idea note that the created waveforms are all different So what about the segments in be
10. RAM exist In order to compensate for shorter note event time as played on the keyboard each of the 32 segments is looped several times before moving on to the next segment this maintains a fairly constant net event length for any pitch Mode 4 uses the entire waveform RAM all 128 segments of it andis always used for sampling since long high bandwidth S o far we have discussed only one Figure 1 INDEX COMMAND CURRENT SEGMENT he m a N 1 Liars 4025 Gre i SB er Gir alee oleh ZERO COMPUTE HARMONIC FADERS MODE s as sia ss S Jum Grant sounds need lots of numbers to represent them So what s the use of Mode 1 Well calculating a time waveform from har monic data can be quite time consuming especially if the supplied data is detailed and enables subtle nuances of sound to be generated However more often that not only a simple waveform is required and to calculate the RAM waveform for all 128 segments when a short loop is all that s needed is rather wasteful to say the least There s no hard and fast rule about which Mode a sound should be in the choice is entirely the musician s However using a voice as the destination for sampling data always results in all 128 segments being overwritten even if the voice selected is Mode 1 Page 5 Figure 1 shows a typical Page 5 display This page displays the harmonic overtone series as a set of 32 faders similar to those on a
11. Touching any of the highlighted options with the lightpen results in the Help sheet specific to the selected option being loaded and displayed The user can flick backwards BWD forwards FWD or recall a previous place PRE commands can be entered from the Help sheets while viewing their correct format The CMI then automatically reloads the display page that called the Help sheet in the first place and executes the command And yes there are even Help sheets that explain the use of the Help sheets That about wraps up the first part of what will doubtless become a saga of some duration Next month we ll take a look at Page 3 the keyboard map and the waveform display page Page D Jim Grant E amp MM 29 COMPUTER MUSICIANS THE FAIRLIGHT JHICIPIGAICIN IID The second part of our insight into one of the world s most popular computer instruments looks at display pages and what they tell CMI owners Jim Grant eral software concept of the Fair light and how much of its power lies in its ability to present its functions to the user as a group of related files called Pages We saw that the CMI powered up with the Index Page Page 1 and that sound and music files were managed by Page 2 One of the problems associated with most sound generating equipment is the way in which the sense sight is excluded from the process of sound formation Most instruments operate on g ast month we de
12. a quick glance at Figure 4 This shows that zero amplitude corresponds to binary 0 while maximum negative excursion is 85 INDER COMMAND Q 114 PAGE D READY WAVEFORM DISPLAY FORMAT E END SEC ME Figure 11 INDER VOICE 1 PAN COMMAND WAVEFORM DISPLAY DISPLAY FORMAT B END SEG BRE 64 32 STEP g INDEX COMMAND WAVEFORM DISPLAY DISPLAY FORMAT 8 END SEC WR 64 32 SitP He VOICE 1 INTEK TEST COMMAND D MODE 4 OIsPLRY AZ _ SSS SSS SS AATA n gt Figure 12 SS Figure 14 WAVEFORM DISPLAY END SEG 64 32 STEP E 8 FORMAT UTEE E TESTA MODE 4 D represented by 1111 1111 or 255 and the maximum positive value is held as 0111 1111 or 127 Still confused Well the value of the Most Significant Bit holds the key If that value is 0 the waveform is positive while a 1 gives negative excur sions Anything else in between is in simple proportion This form of represen tation results in a ratio between the smallest and largest signal that can be handied or in other words dynamic range of about 48dB You might con sider that to be not a particularly impres sive figure since it means that at low signal amplitudes the sound is more or less surrounded by hiss The fact is storage in one form or another of low amplitude sounds is a perennial engineering problem to which
13. amp MM nel allocation and keyboard maps Figure 5 shows a typical display with eight separate voices loaded into the CMI Registers A to H are groups of one or more of the eight Channels and NPHONY is the number of notes that can be played with the sound held in a Register A quick look at Figure 5 reveals that there are eight active Registers each holding the voice indicated In this case all eight Channel cards hold a PAGE D READY x x unique sound and therefore the maxi mum number of notes that can be play ed on the keyboard with any single sound is one This is indicated by the corresponding NPHONY If a single eight note polyphonic voice is required only Register A will be active and Chan nels 1 to 8 will be allocated to A The active Registers are mirrored on Page 2 so that they can be loaded with sounds from disk The Fairlight will flag an error es 1 TRUMPET MODE 4 WAVEFORM DISPLAY DISPLAY FORMAT A B END Figure 4 PACE 3 READY REGISTER NPHONY EDD STICK BASiGT STRMIDI STEMIDE CBELLOOG TANN GANGSA O NDAN BG h ee A B C D E F G H OCT SEMI KEYEORRD CONTROL 1 SAY B 2 SNARE C 3 BODRUM D 4 ORGAN A Figure 5 4 1 4 6 4 a 4 8 KEYBOARD CONTROL KaD TOO SELECTION MASTER TUNIN 3 E MASTER SLAVE PITCH 128 SCALE 12 ary Figure 6 message if you try to open another Register or increase the NPHONY bey ond eight A simpi
14. analogue synths even if the ultimate sonic potential isn t as great Fortunately the Fairlight s internal configuration side steps most of these operational problems and a good ex ample of how this is done is the ADD command This takes a choice of seg ments from one loaded voice and adds RA WAVEFORM DISPLAY VOICE i ADDCOM MODE 4 DISPLAY FORMAT BB END Figure 1 INDEX tis PAGE D READY 804 uo COMMAND LI SINE WAVEFORM DISPLAY ISS Sy DISPLAY FORMAT Q B END SEC FR 64 32 STEP H 8 SSS SSS SSS SE RRRRROO STAs was ANH S ISSS AAA SRA Figure 2 Figure 3 them directly into the same segments of the currently selected voice scaling the amplitude to avoid clipping if necessary If you were to ADD all the segments into another playing the keyboard would result in both sounds being heard together but only using one voice Figure 1 shows a square wave and Figure 2 a sinewave both resident in different chan nels of the CMI the result of ADDing them together is shown in Figure 3 The addition s proportion can be varied by f using the GAIN command prior to the action or by repeatedly ADDing one r voice to another to increase its amplitude relative to the composite sound RAAY 1005 ERKAMA COMPUTER MUSICIAN OWN 1111 DISPLAY FORMAT Voice a minimum MSB 1 111 1111 Triangle Figure 4 Linear conversion
15. graphic equaliser Each fader is logarithmic in nature and has a range of zero to 255 allowing a good degree of control over harmonic amplitudes and thus enabling the application of a Fourier type harmonic series As an example Figure 2 shows a square wave generated by the CMI com puted from the values of Fourier com ponents shown on the faders The result VOICE 1 SQUARE l ant waveform is visually very similar to the real thing and perhaps more importantly sounds indistinguishable However the power of the CMI lies in its ability not only to compute a complex waveform from a set of Fourier com ponents so that it can be played on the keyboard but also to compute a different waveform for each segment Every seg ment has a unique Page 5 display so while a Mode 1 sound has 32 sets of faders a Mode 4 one will have 128 The current segment number is indicated on the display and this allows a synthesised sound to change drastically throughout Figure 2 Rote Et ints PRR 2 ee 5 88E mernonic 3 MELE KeanEny Stcrcnt ft i razsserashiiiigt zeeo commute its duration simply by the user filling each segment with a different waveform calcu lated from its own Page 5 fader settings In fact the technique of using different waveform segments as the sound pro gresses is very much the domain of PPG synthesis Generally speaking these pro gressions are known as wavetables an
16. in this case 0 255 eight bits two things suffer noise and dynamic range The noise is only heard when a sampled sound is actually being played through a DAG ie the ADC and DAC are notin themselves inherently noisy Making sure that the peak of the input signal causes the maximum ADC code to be generated ensures that most of the noise is masked by the volume of the signal on playback The Display box in Figure 1 is an invaluable aid in this respect Dynamic range on the other hand is a measure of the range of different amplitude values that the ADC can handle In a linear system this is directly related to the number of bits used in the process and roughly speaking the dynamic range of the sampled signal is 6dB times the number of conversion bits Since the Fairlight uses eight bits this gives 8 x 6dB 48dB dynamic range Companding techniques result in a larger dynamic range about 70dB for the same number of bits used but at the expense of greater noise at low signal amplitudes The reasons for Fairlight s choice of a linear converter will become more apparent when we took at the functions on Page 6 The actual sample rate is very cleverly generated on Channel card 1 Normally the onboard circuitry is used to generate the E amp MM OCTOBER 1984 correct clocking rates required for digital to analogue conversion when a keyboard note is pressed However for the duration of the sampling period the CPU grabs Channel
17. mix we d get the product and end up with VCA type effects at low frequencies and strange sidebands at higher ones Which isn t all things considered a particularly desir able state of affairs Mixing Anyway enough of the lecture and back to the Fairlight The MI X command can also drastically alter the waveform RAM Essentially it generates a cross fade between two specified segments which must not be adjacent ie there must be at least one segment in between The waveform memory of each segment between the start and end points con tains a proportion of the existing wave form in that segment and that of the end segment this is best illustrated by examining Figure 6 and Figure 7 for before and after views Remember that the new contents of each segment is a mix between where you are in the waveform and the destination segment Thus from Segment 2 onwards the waveform simply fades up to a square wave MIX is most commonly used to add a clean fadeout to a sound that decays to noise or doesn t decay pro perly in 128 segments Have a look at the percussion sound sampled using Page 8 and shown in Figure 8 It s pretty clear that the sample ends in a dither of noise Now suppose we needed nothing more than a short percussive strike and that only the beginning of the sound was of any interest to us A quick solution would be to turn to Page 6 and ZERO say Segments 64 to 128 halve the sound and then MIX from Se
18. par SAUNE SANPLI tials A SAMPLE LEVEL But Page 6 waveform drawing is of TRIGGER LEVEL enormous help first because it gives the TRIGGER DELAY user extensive and direct control of waveform RAM with one sweep of the hand and second because the ability to bring about such drastic sonic change so simply and visually almost artistically some might say is a practicality light years away from the sophistication and complexity of the underlying machine and its software Or to put it another way it makes the CMI seem less of a beast and more of a pet The Practical Approach fome Sir PACE READY ttt Alteration of the display image is not punta reflected in the waveform RAM until the FILL command is used This allows the reverse video field to be used as a scratchpad area in which waveshapes TARRE MAFIMEA Figure 4 SOUND SAMPLING SAMPLE RATE FILTER LOW FILTER HIGH SAMPLE LEWEL TRIGGER LEVEL TRIGGER DELAY 14050 He t can be developed before they are finally committed to RAM Looking again at Figure 1 notice there are two slider controls similar to those on Page 5 These control the segment number to be displayed and the stepping rate through the entire memory instigated when the command Step is issued Also shown are three classic waveforms triangle sawtooth and square which deposit a perfectly fitting single cycle wave into the segment The pulse width of the square can be varied fro
19. rep resentation of a desired waveform does not require an infinite number of sine waves more than 16 is enough to give a good approximation The Fairlight uses a maximum of 32 harmonics which enables most waveforms to be synthesised with a fair degree of accuracy Figures 5 to 8 show the development of a square wave by successively adding further harmonics and using Page 5 to compute the resultant waveform The square wave doesn t con tain any even harmonics 2 4 6 and so on and we can see that the lower harmonic numbers set the basic square shape while the higher ones fill in the bumps and sharpen the edges Even with all the odd harmonics the Fairlight can compute the square wave is still not visually perfect but it sounds OK a E amp MM DECEMBER 1984 Figure 3 INDEX COMMAND DISPLAY FORMAT E END EG 123 CONTROL PARAMETERS CONTROL FILE MODE EXP LEVEL FILTER DAMPING ATTACK 4 GLISSANDO OFF PORTAMENTO KEYVEL SPEED it CONST TIME 100 VIB DEPTH VIB SPEED WR VOICE 1 SWEEP co LOOP CNTRL LOOP START LCOP LNGTH START SEG SLUR SUSTAIN ON CNTRLI i CNTRLI OFF OFF CNTRL Lz 2 amp 8 SWTCH Pe ee te Oh GPF ERG KEYVEL Figure 5 Figure 6 awn tonnan test HARMONIC FADCES nost t CURRENT SEGMENT WITT iI iii HAHH sec EPEC STEER RGR 14 ee Figure 7 Figure 8 THIET VR TT CORMAND test MABR
20. shows one of the Help sheets for Page 7 which provide a quick reference for the range and possible patches available Some of the control parameters are self explanatory such as Level Vib Speed and Vib Depth Again we come across the enigmatic Mode switch which is best left until Pages 4 and 5 are discussed the suspense is killing me Ed EXP is the other half of the com panding process that was an option on Page 8 discussed last month As you may remember it s a hardware option and is very rarely fitted to the CMI due to the non linear sampling data that HHA Wilt Sm erat results from its use The Filter is a low pass tracking filter resident on each Channel card used to attenuate any unwanted high frequency content present in the voice the cutoff fre quency is raised by simply increasing the value It s all really a case of swings and roundabouts a high filter setting gives a bright realistic sound but often with digital birdies warbling in the background while low filter values suppress any funnies but reduce the sound to a dull noise When Portamento is on each Chan nel allocated to the voice produces a continuous glide between each new pitch it is to play and the last pitch played the rate of note glide being set by the Speed control Glissando dif fers from Portamento in that the glide is not continuous but chromatic and all the notes on the keyboard
21. that doesn t contain a whole number of cycles the ends of the loop won t join up without causing a sudden jump in amplitude Choosing an inappropriate sample INDEX PACE 8 READY OPE Ee COMMAND MARINS SOUND SAMPLING SAMPLE RATE 28160 HE SAMPLE LEVEL ess FILTER LOW i TRIGGER LEVEL 3 FILTER HIGH E TRIGGER DELAY M COMPRESSOR OFF SAMPLE DISPLAY Figure 1 INTE COMMEND FISFLAY FORMAT A B j 4 AN E ENNAN Ny ests e Figure 2 INDEX PAGE D READY PLE s COMMAND LTUNE MODE 4 WAWEP ORM FORMAT A B END a DISPLAY OCTOBER 1984 E amp M ce A COMPUTER MUSICIAN rate results in a dreadful glitch which increases at a rate proportional to the pitch played on the keyboard If the sample rate is almost right a one segment loop produces a sudden slight pitch shift and waveform crests and troughs drift laterally through a Page D display This is shown in Figures 2 and 3 where a drift to the right sharp is caused by the sample being set too high and a drift to the left flat by it being too low Figure 4 shows a sound which is in tune with the system and therefore loops perfectly At the other end of the scale if the sample rate is totally wrong the display becomes a hopeless jumble Figure 5 The relationship between a whole number of cycles and each segment of waveform RAM is also the relationship req
22. that for next for example as a tone burst can be recorded month B INEEX PAGE D READY Xxx WEE T COMMAND THTUNE WAVEFORM DISPLAY ie DISPLAY FORMAT A END SEG MI 64 32 STEP ia ae INDEX DISFLAY FORMAT A END SEG Fie PAGE 8 note A 118 Hz 14896 Ae 14317 E 15804 16744 C 17748 D 18795 De 19912 E 21038 F 22351 FH 23688 G 25088 Ge 26586 Sa Fee TOF Fut but SAMPLE RATES va 2va 28168 a46 29835 7459 Sa 730z 29 ae 41 Sor 44 397 46 9956 49 14648 5a 11175 5 118448 12544 13254 87 COMPUTER MUSICIAN THE FAIRLIGHT JIC IP Ly A JILIN 18310 How the CMI provides for special effects and looping in a language just about everyone can understand Jim Grant Fairlight s main sound creation methods sampling The simple act of pointing a microphone at a sound source and typing S on the alphanumeric keyboard transforms the Fairlight from an expensive computer into a powerful musical instrument And the keyword here is musical The ability to create new and interesting sounds or indeed sample them is not in itself enough What is required is contro over that sound and to coin a popular phrase the control must L ast month we dealt with one of the _ be real time Musicians of course call this control expression and it s a par ticularly difficult feature to build in
23. CMI it will pull in a specified control file if it was previously Linked to the voice using the command LNK At the bottom of the display is a box which indicates currently loaded voices The control file may have a different name zx from its intended voice so the two are differentiated visually The active control file is the name highlighted while the active voice is shown in the top right hand corner Other control files can be inspected by pointing the lightpen at the names in the display box or by typing Vn where n is the voice number There are six real time faders and five switches patchable to most parameters Thr e of the faders and two of the switches are on the left hand side of the music keyboard while the other faders or footpedals are accessible via Cannon type connectors on the rear of the key board In addition the music keyboard passes key velocity information to the CMI and this can be patched to Level and Attack as KEYVEL Below the voice list in Figure 1 is a complete list of the controls and switches that are available This is used in conjun ction with the lightpen and provides a quick way of patching the controls to various parameters the lightpen is pointed first at the parameter and then at the control list A patch can also be estab lished by tabbing a cursor around the display using the QWERTY keyboard and typing in the appropriate name or numeric value Figure 2
24. OMIC FARES T pi UT bhi CnEN HART paaaservesd Tibi eddd zero Compute TRICK COMmanD p2zaece zeno ii comPure AERONIC FROLES BRUSE UE il ent 1 iit resdbi bb ied id bid ijid iiil Fh 101 THE FAIRLIGHT JIE IGA ICIN HJD COMPUTER MUSICIAN Waveforms lightpens and interpolation all come under examination in this instalment of our Fairlight CMI Grand Tour Jim Grant open up a copy of E amp MM without reading anything about the world s most influential computer musical instru ment your intrepid reporter returns from a New Year hangover with another action packed episode This month we look at the information presented by Page 5 ina slightly different light You ll remember that Page 5 held the values for 32 harmonic faders and computed the result ant waveform for the current segment You should recall also that the only way to create a complete sound of 32 segments was to define the fader levels for each segment and compute over the whole waveform or define a few segments and Fill the harmonic data to the rest of the segments before computing It s not hard to see that this method of creating sounds may be very precise but can also be extremely tedious In a lot of cases all we need is a way of tailoring the harmonics as the sound progresses harmonic envelopes in other words
25. THE FAIRLIGHT JCP Ln AIIM LHI When the Fairlight CMI was released seven years ago both the machine and its software represented a significant step forward in the application of computer technology to music Today the Fairlight is used in the making of popular music the world over as well as performing an important role in the field of musical and technological education Despite this very few people are fully aware of what the CMI does and how it does it Jim Grant who s been working with one for a number of years at the London College of Furniture has decided to rectify matters by writing a series dedicated to explaining the Fairlight s workings Part one appears below tasara E amp MM AUGUST 1984 27 most computer music systems were the perogative of mainframes and their contribution to the world of everyday music was slight Kim Ryrie the Fairlight s father and his Australian colleagues soon changed all that how ever and their invention ts now used in almost area of music production to the extent that many people appreciate its sound without realising that they re listening to music by numbers However despite its widespread use there are relatively few Fairlights in general circulation less than 100 in the UK and to see one in action at close quarters is a real treat Herein lies the rationale for this sertes of articles What does the Fairlight do How does it do it And what can the av
26. a Page A Page has one or more files resident n the Systems disk which are loaded when the Page is selected Page 1 is the Index Menu itself Figure 1 while Page 2 manages the files stored on the disk in the right hand drive Drive 1 These files are user created and there are seven different types as indicated by the suffix after the file name These are as follows NAME VC is a voice file occupying about 20kBytes It holds waveform data 16K and extra information regarding looping and so on NAME CO holds control information such as portamento vibrato frequency and depth 28 INDEX COMMAND np we D Dario a Pw a o a l un NAME INDEX BISK CONTROL KEYBOARD CONTROL HARMONIC ENVELOPES WAVEFORM GENERATION WAVEFORM DRAWING CONTROL PARAMETERS SOUND SAMPLING SEQUENCER ANALOG INTERFACE COMPOSER WRUEFORM DISPLAY DISK LIBRARY RERL TIME COMPOSER SCREEN PRINT JIM GRANT _ mu AO am DAD DHA Dts De AS ceo On zo 4 oy DO zvoz TETE am E UN A OPO 10 O N D N A w e ONOHO NN O wW w cC U ZIM Ae SIO Ci OCrNMoOZzzZooO rwupr o o oa GO RIAN PID DO PG PO DD fr ee e aee O O O N D N e w e A a a N AHAHONWAN DOU DOZDA CcetZzwxt lt DDVDOKHAZH ZZWAGZZMOOG IMCs mM ADAMHAaMMMCDMlmMG Nee Tel TrwanK O mezx ONNUM UDR VVAMUW MWNUNONMHANXXXMNDODSO 1 1 1 t t R REGISTER DEOD fl fF EH TRANSFER LOCUST us DELETE IN type INSTRUMENT Voices BOD2 STRMID EXAMPLE OF PACE 2
27. between the start and end notes are played If both Portamento and Glissando are selected Portamento takes preced ence Constant Time is a switch which selects between two types of glide when it s turned on the same time is taken to travel any musical interval and the rate of change alters according to that interval hence the name Constant Time This results in polyphonic portamento or glissando in which the notes arrive at their destinations at the same time prod ucing a coherent chord With the switch off the rate of change remains fixed determined by Speed and the time taken to glide varies with the size of the interval Attack and Damping The Attack parameter has a range of zero to 16 384 milliseconds and may be patched to KEYVEL for touch sensitive control of the attack time It s active only for Mode 4 sounds and is extremely useful for imposing a degree of artificial enveloping upon sampled sounds Damp ing has a range of zero to 65 536 milliseconds reduced to 16 384 milli seconds in Mode 4 The value determines the final decay time of the voice te from key release to silence If a loop is active and one or more segments are repeated continuously the voice plays the loop until the damping time expires when the key is released otherwise the voice continues through the remaining seg ments Should the end segment be reached before the damping time expires the voice stops abruptly
28. d in the PPG a sound consists of a set of 64 waveforms that reside initially in EPROM they are transferred to RAM on power up which are read out sequentially when a key is pressed The idea behind this system was to circumvent the need for filters by constructing wavetables that held a set of representative waveforms of say the classic filter sweep Unfortu nately this results in a very hard metallic sound as the sound changes abruptly from one waveform to another slightly different one It s still a good sound but in the interests of flexibility PPG have chosen to incorporate the usual VCFs and ADSRs as well as extensive wavetable modulation The CMI is also capable of this form ut synthesis to a limited degree using the loop controls on Page 7 For example NEMEC AARECR 10RA ERRAR COMPUTER MUSICIAN suppose we had filled all 128 segments with waveforms that change very slightly as we progress through the waveform see Figure 3 Now if the loop controls were set up as shown in Figure 4 this is a Page 7 display moving CNTRL1 on the music keyboard would result in a different timbre when the note was played Using this technique allows for some expressive playing since the principle is rather akin to varying the filter frequency control ona synthesiser the only difference being that the actual timbres can be radically different from one segment to the next To increase the timbral movement withi
29. e rule applies the sum of the active Registers times their NPHONY must be less than or equal to eight Figure 6 shows another example of the Register allocations Here another set of voices has been loaded so the NPHONY and Registers are configured differently Although the Register and NPHONY settings may seem a little confusing and limited the exact con figuration is determined entirely by the musician and changes can be effected very quickly for evaluation Keyboards and Tuning Any voice can be tuned in increments of plus or minus one hundredth of a semitone up to 6 octaves with crystal accuracy Scale allows the Western tempered tuning of 12th root of 2 00 to be changed to any other macro micro tuning eg for quarter tones you simply change Scale to 24th root of 2 00 Pitch is a master tuning control which can vary tuning of all the loaded voices by a quarter of a tone in 256 discrete steps to bring the CMI in tune with other instruments if necessary The Keyboard Maps each consist of a keyboard number 1 to 6 followed by six letters indicating the Register assigned COMPUTER MUSICIAN to each octave As the CMI is a music ian s instrument it supports two six octave keyboards called the Master and the Slave Using the maps it s possible to create eight different keyboard con figurations by choosing which sounds will play on each octave within a key board The Master and Slave can be linked as
30. east 16 circuit cards the exact number depending on various options such as an analogue interface and sync card and eight of these are known as voice or channel cards The Fairlight produces sound by a process called Waveform Synthesis Each command that deals directly with sound generation must invelve at least a section of a waveform The waveform itself is held in 16K of RAM on each channel card as a direct digital representation so that increasing amplitudes give larger binary numbers Therefore when an eight note polyphonic sound is present on the keyboard each channe holds the same voice data Put simply the channel cards can be regarded as digital oscillators whose waveform is determined by the contents of 16K of RAM Figure 3 Different pitches as played on the keyboard correspond to the RAM information being read and converted by a DAC at different rates the channel cards perform this function autonomously The computer section of the Fairlight passes parameters such as pitch vibrato portamento rate and loop ing points along its data bus and once these have been received the channel card outputs the sound until the para meters are updated Overall pitching of the CMI is deter mined by a system clock resident on a special card known as the Master card We ll be referring to this on numerous occasions over the next few months since it holds the circuitry for a good many of the CM s functions A 34MH
31. en the CMI calculates the waveform segment by segment and scales the amplitude so that it fits exactly into the dynamic range of eight bits The ENG profile is also generated and its shape implied by the harmonic data but can be altered by the lightpen to control the amplitude of the sound on playback Auxiliary Functions Along the very bottom of the display Page are a number of useful commands Clear deletes all the displayed profiles from the graph but they remain active and can be brought back to life simply by the programmer selecting the harmonic numbers with the lightpen Delete on the other hand merely removes the currently selected profile The same sort of structure applies to Reset and Zero Invoking E amp MM MARCH 1985 INTEN OME E EN oe PAGE D READY COM At DA CIRE PERIE EPLAN MIDE EE er TNDEX COMMAND CLEAR DELETE RESET Reset causes a confirmation message to be printed and aiso results in Page 4 being restored to a complete default condition Zero isn t quite so drastic and results only in the current profile being set to zero Every time you give a Compute command a new energy profile is generated Scale is the opposite it re draws the harmonic profiles from a modi fied energy profile This is not without its dangers however as it can result in some harmonic profiles being scaled beyond their maximum amplitude which leads to clipping The Fairlight will inform
32. erage musician do with it Bes the Fairlight s appearance Hardware To take delivery of a Fairlight leaves your bank balance empty and your living room full The hardware consists of a Central Processor Unit CPU one or optionally two six octave keyboards a typewriter style QWERTY keyboard and a VDU with added lightpen In addition there are some long connecting leads a Systems floppy disk drive and a box of disks containing library sounds Software A foolproof system of connectors and a quick glance at the manual on the part of the user ensures that the Fairlight can be powered up in no more than five minutes The VDU displays the expectant message CMI READY while the CPU hums quietly there are three fans pulling air through the innards keeping 500 watts of power dissipation down to an accept able temperature Inserting the Systems disk in the left hand drive Drive 0 results in a faint click as the stepper motors engage The operating software is loaded as a series of fetches each section of program loaded pulls in the next section When this process has been completed the user is faced with the Index page See Figure 1 Here lies one of the Fairlight s most powerful features The whole system is menu driven and the different options correspond to different VDU displays and sets of commands which are entered from the alphanumeric keyboard Each option is referred to as
33. etailed harmonic micro surgery of the sound Remember though that not every sound is created from harmonic data so that if for instance you re working on a sampled sound salling up Page 4 will result in a completely lank profile graph More About Mode One of the previously mentioned features of a Mode 1 voice is the way in which the first 32 segments are looped several times to maintain the net event time of the sound across the keyboard In fact we have some control over how long a segment lasts before everything moves on to the next one and this is accom plished via the profile Figure 4 shows a harmonic profile graph with the duration profile indicated by a double line the default value is approximately 50mS per segment and increases as the profile is drawn higher up the graph This is parti cularly useful for creating sounds with a short click at the beginning of each note such as that of a Hammond organ A very short duration value can be drawn for the first one or two segments and then a longer profile for the remainder of the sound If the duration profile is made zero the sound degenerates to a Mode 4 condition except that it only lasts for 32 segments Another interesting aspect of Mode 1 sounds is their ENG profile This is an artificial envelope that s superimposed on the waveform in much the same way as the more usual ADSR principle But this one s a lot more flexible When the Compute command is giv
34. first harmonic does one cycle the second harmonic two cycles and so on Gone are the Bad Old Days of trying to sample a sound to make it fit segments evenly All you have to do now is use any old loop to span the sections of a wave form that are of interest and Bob Moog s your uncle Next month yes there s still more to come we ll take a look at Page 6 which among many other weird and wonderful things allows you to splice a sound down to no more than 16 384th of its length And you thought a razor blade was powerful z 87 JGWCIPILAIIN GID When a CMI page is as helpful a source of music graphics as Page 6 you can bet your life it needs a lot of explaining so this month s episode is dedicated entirely to it Jim Grant on the Fairlight whether it s from existing sampled data using Page 8 or harmonic profiles generated on Pages 4 and 5 you can be sure that Page 6 will be referred to over and over again At its simplest level Page 6 is a static oscilloscope containing one segment of the waveform RAM Like Page 4 the large black area is a reverse video image and represents the region that can be hit by the now infamous lightpen But unlike an oscilloscope which acts only like a window on the information Page 6 in conjunction with its commands and light pen behaves more like a door through which we can directly access the wave form data The Manual Approach Regular readers of this
35. gment 45 to 64 Looking at Figure 9 shows the result a sound that dies away evenly to a noise free end much to the relief of all concerned MERGE is fairly similar to MI X with one fundamental difference Again a form of crossfade is generated between start and end segments but this time the previous contents of intermediate seg ments don t figure in the result Quite simply the segments in between contain a decreasing proportion of the start segment and an increasing proportion of the end segment Figures 6 and 10 oh yes very logical Ed reveal all The MI X and MERGE commands are tremen dously powerful for splicing together sounds of differing origins and producing an even fade from say a violin bow attack to a sung ahh Creating a Sound So now that we ve discussed most of the commands available let s try to create a sound using everything except the Fairlight s Page 8 sampling facility The question is am allowed to use Page 2 and pull a sound off disk to work with Well I ve decided I ll have to cheat a bit because already have a thoroughly marvellous sound called PAN VC which attacks with the characteristic breath chiff of pan pipes MAY 1985 g E amp MM First off we configure Page 3 to generate two voices one with an NPHONY of 7 in Register A to be played on the keyboard the other monophonic in Register B as a scratchpad voice Using Page 2 we load Register B with
36. he M I X and MERGE commands Fairlight deci ded to bung it on Page 6 alongside them However rather than discuss the re maining Page 6 commands in any detail right now think it s probably best for all concerned if t demonstrate their power in the context of a typical edit session in which a sound is created from scratch ie without any sampled data So now you know what I ll be talking about next month a 5 44 RHY EFFECTS ONLY LIMITED BY YOUR IMAGIN ATION PAH L SOME_ STRING AND BRASS PRESETS A TOUCH OF ORCH 5 AND SOME SCRATCHING S MINUTES LATER ANOTHER MASTERPIECE FINISHED THINK I LL JUST D FOUR REMIXES OF THIS ONE GIVES ME A HEAD ACHE JUST TRYING TO THINK DOWN TO HIS LEVEL a j FOSTERLITE CMI THE FAIRLIGHT BXPLALITIED In which we take a look at the difference between linear and logarithmic conversion and incidentally end up creating a sound using the Fairlight s synthesis facilities Jim Grant ost people involved in the modern M music industry are already aware of the Fairlight s incredible poten tial as a music production tool These days you switch on the television radio or record player in the almost certain knowledge that a CMI will make its presence felt somewhere along the line and when you consider just how useful its specification is to studio engineers and producers that s hardly surprising Even in 1985 there aren t many machines capable
37. m 1 to 99 by changing the value held next to the square wave symbol Auxillary Commands In addition to the graphic capabilities of Page 6 there are anumber of commands that can only be entered from the Fair light s alphanumeric keyboard Figure 2 shows the range of functions available as presented by the HELP sheet menu First off are a f w utility type com mands GAIN scales the displayed data by a specified percentage if the rescaled waveform is about to exceed the ampli tude range of the system the CMI will ask you whether or not you want to proceed and thereby induce clipping If you reply in the affirmative the command will be duly executed Meanwhile the INVERT command inverts the phase of the wave form this is useful as a prelude to some of the other functions such as MIX MERGE and ADD A particularly neat little command is ZERO which allows us to create a null voice in preparation for the ADD com mand The entire waveform RAM can be F AHIGETTING A BIT OVERDRAWN AT THE BANK TIME TO COMPOSE ANOTHER MEGA SMASH HIT SINGLE THINK Kinja WITH E amp MM APRIL 1985 PANT THINK COMPRESSOR OFF SAMPLE DISPLAY Figure 5 turned end on end by using REVERSE and this results in the backwards sounds that have become familiar to pop music followers the world over REFLECT is a less commonly used but if anything more interesting variation on this theme It allows us to place an imaginary mirro
38. me time the music keyboards are scanned for pressed notes key velocities are calculated and the control sliders and switches read At the right hand end of the Master keyboard is a calculator style keypad and alphanumeric display used for rapid loading of voices in a live situation Music keyboard information has the highest priority of all data in the CMI which responds instantly to the packets of data sent flying down the cables at 9600 Baud Well that about finishes off our des cription of the utility type display Pages In case you re wondering what the Mode setting on Page 3 is for don t worry all will be explained Next month the controls on Page 7 and sampling on Page 8 a COMPUTER MUSICIAN THE FAIRLIGHT JGIBCIPILAICIN JHI Part three and a discussion of how the CMI samples a sound and why its own particular sampling techniques are employed Jim Grant basics to concentrate on the more interesting sound creation Pages Now the single feature that characterises the Fairlight in many people s minds is its ability to sample natural sounds this aspect is dealt with by Page 8 and is surprisingly simple to use At the rear of the CMI lies a selection of line and mic inputs to suit most applications That about takes care of the hardware because everything else is dealt with by software Typing S or touching Sample with the lightpen initiates the sampling p
39. n a sound CNTRL2 can be patched to LOOP LENGTH on Page 7 resulting in sections of different waveforms being read out repeatedly Since the waveform data is computed by the CMI it s always constructed so that the waveform fits exactly into one segment thereby over coming looping problems Fourier Series Well with all this talk of Fourier com ponents and the like some of you may reasonably be thinking what s it got to do with music The answer of course is not much Only scientists and engineers delight in quantifying the world which our senses seem to handle perfectly ade quately However in order to express ourselves explicitly and unambiguously about a wide variety of concepts some of which may be abstract we need to use the language of mathematics Fourier analysis and synthesis are mathematical statements about something which is not intuitively obvious the fact that any truly periodic waveform can be decomposed into an infinite sum of sinewaves usually called harmonics Similarly any periodic waveform can be constructed from the sum of an infinite number of sinewaves The sinewaves have frequencies that are related to the fundamental of the waveform in such a way that the second harmonic lies at twice the fundamental frequency the third harmonic lies at three times the fundamental and so on The fundamental itself is often referred to as the first harmonic Of course obtaining a reasonable
40. o 128 sections called segments Each segment consists of 128 bytes so the waveform comprises 128 segments multiplied by 128 bytes to give 16384 bytes ie 16K This saves the musician handling unwieldy computer numbers when dealing with the waveform RAM The display shown in Figure 1 is a psuedo 3D representation of the voice called TRUMPET Each line from left to right is a segment and the foremost segment represents the beginning of the sound When a keyboard note is pressed the CMI reads out the RAM information segment by segment from the front to the rear of the display There are two display formats A and B and a number of options within each type Figure 7 is in format A and seg ments 1 to 128 are shown in steps of 4 Figure 2 is again format A with the end segment number 32 and steps of 8 therefore only five segments are shown Format B gives an oscilloscope type display but with each segment slightly above the preceding one Again there are a number of display options Figure 3 shows TRUMPET segments 1 to 128 in steps of 2 and Figure 4 segments 1 to 64 in steps of 8 Although Page D is purely for display purposes and does not support any sound creation commands it s still an invaluable aid At its most basic level it answers the questions where has the sound gone and is the waveform zero Page 3 Page 3 is another utility type display Page It deals with voice tunings Chan SEPTEMBER 1984 E
41. of spreading six octaves of sampled sound across the keyboard and manipulating that sound within user sequences to the nth degree of precision But if you re fortunate enough to sit in front of a CMI for any length of time without any production deadlines to meet you ll soon discover that its creat ive power lies as much with sound synthesis as it does with music produc tion per se Pages 4 and 5 are good examples of this in that they offer the fairly standard synthesis tools of har monic sliders and profiles but Page 6 which we introduced last month is something of a software oddity since it allows control over the whole waveform from a single byte to macro type com mands such as GAIN MIX and MERGE Now for any command or process to be really useful in the field of sound synthesis it must be responsible for some radical change in the sound struc ture that s both intuitive and easily understandable For example the VCF of an analogue synth changes the sound a great deal and can be simply explained and understood in terms of the attenu ation of harmonics FM synthesis on the other hand also results in vast timbral differences but comprehension of the processes involved and their possible results is a lot more difficult That s why actually arriving at a pre specified sound on something like a Yamaha DX7 requires so much in the way of practice and patience and why so many musicians prefer programming
42. r in the sound and reflect every part of the waveform in front of this mirror to waveform RAM behind it Take a look at Figures 3 and 4 for before and after views the mirror is at segment 64 Now on to another of the seemingly insurmountable problems brought on by the onset of new musical technology Very often when a sound has been sampled the beginning of the captured data does not occur at exactly the start of the RAM perhaps due to some extra neous noise pretriggering the ADC How ever if the effect isn t too severe a convenient method of correction is to ROTATE the sound within the waveform RAM to bring the start in line with byte 1 This has the often desirable side effect of shifting the first part of RAM to the end See Figures 5 and 3 for another revealing before and after picture imagine NOISE will be fairly self explanatory to even the least clued up of this column s readers it fills sections of the RAM with the output of a random number generator hidden inside the soft ware Funnily enough the GAIN command is also used to tailor the amplitude of the noise to that of the rest of the sound Now BLEND is a strangely out of place command Personally think it should be on Page 4 since its role is to help smooth out glitches caused by imperfect looping points It may be that to find a good loop it makes extensive use of extrapolation techniques and that see ing as this is a central feature of t
43. request the replacement of the system disk name and suffix as file on DISK AJ See also MENSIS PROTECTION T lt return gt When the message appears place a file disk Replace system disk when completed without your consent TO COPY an ENTIRE DISK TYPE If a file already exists on DISK B has same it will NOT be overwritten in LH drive New disk will usually show an increase in FREE SPACE available NAME IN configures the CMI to a parti cular instrument state Voices are auto matically loaded and spread across the keyboard NAME SQ holds polyphonic keyboard sequencer information NAME RS is a real time sequencer Page R file NAME PX corresponds to a screen dump Page S to disk This can be spooled later to a dot matrix printer for hard copy NAME PC PT SS are Music Composition Language MCL files These are gener ated on Page C and hold text files that describe notes with duration dynamics and so on A voice file can be loaded in a number of ways Probably the easiest is to point the lightpen at the voice name and then at the command LOAD at the bottom of the display Figure 2 Drive 1 springs into action immediately and after a second or two the selected voice appears on the keyboard So far so good But where does the voice information go and how does it result in a sound when the keyboard is played E amp MM AUGUST 1984 Channel Cards Inside the Fairlight there are usually at l
44. rocess After a second or so the Display box shows the sound envelope for quick monitoring of input levels See Figure 1 If all is well with the Keyboard Maps on Page 3 the sampled sound will be playable on the music keyboard So far so good But what are the other functions for Well some of them are self explanatory Sample Leve is a software based volume control and can be used to attenuate signals that exceed the input range of the Fairlight Unwanted frequencies can be rejected by using digitally controlled high pass and low pass filters their cutoff points are set by Filter High and Filter Low The actual circuitry lives on the ubiquitous Master Card and takes the form of switched resistor networks using the much loved CMOS 4051 chip Whenever a signal is converted to a stream of digital numbers it s necessary to bandlimit it to one half or less of the Sample Rate Stated simply this means that we must have at least two sample values of the input signal s amplitude for the highest frequency present if this condition is not met the information that the sampling process has captured is not sufficient to reconstruct the original signal without frequency distortion This type of distortion is known as aliasing and is both extremely noticeable and rather unpleasant The CMI guards against aliasing by incor porating tracking filters controlled by the Sample Rate A t last we ve covered enough of the CMI
45. scribed the gen INDEX COMMAND END SEL Figure 2 esc wl Lee Ey NER LOMNMAND E t WAVEFORM DISPLAY eS JEISPLAY FORMAT A END SEC WB 64 327 STEF 1 4 8 Figure 3 86 SEPTEMBER 1984 E amp MM COMPUTER MUSICIAN the basis of the user twiddling the con trols and stabbing the keyboard Fair enough of all our senses the ears are by far the most acute Yet if we consider all the electronic music equipment cur rently available the most user friendly instruments have graphic displays per haps in the form of panel legends and LEDs or liquid crystal display Despite the fact that sight is a very poor quali tative sense it can be of enormous psychological help in our field Basically it boils down to If can see it can understand it Page D There s no doubt that the Fairlight s visual presentation is founded on this premise Each display Page is graphic without being ostentatious and Page D the voice waveform display is a prime example of this Typing PD followed by a RETURN on the alphanumeric keyboard will result in a display of the type shown in Figure 1 To appreciate the signifi cance of the display we must delve a little deeper into the workings of the CMI Remember that voice information is held in 16K of RAM on each channel card To simplify matters the CMI div ides the memory and thus the wave form int
46. series will pro bably recall that each segment consists of 128 bytes and that each byte can hold a range of values from 128 to 127 giving a grand total of 256 possible values Now we can highlight any particular byte by positioning a narrow vertical window over the display area The byte in question shown in Figure 1 has its position indi cated by POINT and its value by LEVEL these can be changed by typing in different values from the alphanumeric keyboard So theoretically at least you could type in 128 levels for each byte shown in Page 6 and repeat the process for all 128 Page 6 displays to cover the entire sound giving 16 384 levels in all In practice though such a feat would take an unbelievable amount of manual labour exactly what much of the Fairlight s software was designed to eliminate to achieve and this has led me to wonder whether this feature will be dropped when the Series Ill Fairlight complete with waveform RAM of megabyte dimen sions makes its appearance later this year A more practical approach is of course to make use of the lightpen This is as simple as drawing on the back of a bus ticket but just in case even that is beyond the user s artistic capabilities the JOIN and PLOT functions also present on Page 4 are available here too to help out with the drawing of geometric shapes In fact trying out a few sample sket ches soon reveals that waveforms which look drastically different may
47. shown in Figures 5 and 6 to any map by changing the Selection numbers The information presented in Page 3 is known as an Instrument file The file can be saved on the user disk and is given the suffix NAME IN When this file is loaded it will pull the specified voices into the CMI allocate the Registers automatically adjust the tuning and spread the sounds across the key boards Instrument files are a usefully quick way of bringing the CMI up to a playable state with preset voices and tuning Hardware At the time the Fairlight was designed the microprocessor was considered to be a medium to slow speed device To increase the power of any computing system designers have two basic choices One of these the Synclavier approach is to base the instrument around a dis crete logic minicomputer thus utilising the raw speed of logic chips This is quite an elegant solution since music by numbers requires lots of number crun ching but the other choice and one which is becoming increasingly popular is computing concurrency In a basic CMI system there are four micropro cessors of the 6800 family Two of these are in peripherals ie one each in the music keyboard and the alphanumeric keyboard and this means there can be several independent processes being executed concurrently The microprocessor in the alpha numeric scans the keys and passes the data to the music keyboard when requested At the sa
48. sound sur prisingly similar Scientifically speaking this is probably due to the fact that as a f you re trying to create a new sound 98 INDEX COMMAND te STEFF RATE START SyoOF Figure 1 sheet Pe ren eA E ee Figure 2 tx PAGE 6 READY x WAUEFORM DRAWENG CURRENT SEGMENT JOIN FOIN LEVE DISFLAY ZERO FILL INVERT ZEOMPUTER MUSICIAN THE FAIRLIGHT sem a04 i E HAWES PLOT 7 L GRAFH SEGMENT stzianment command Wy stecpina diselay form modification aveform modificati tf CURRENT DISPLAY Ma sonnand QUAI connard LETT eseetorm generation FRO command GM commana MERGE conn and EE command ROTATE comm srg REFLECT command A scnimand TRAI command inh era Lhe trae nt IER Tepes aes FEGE touch MAS cr and vores A Kt ze Where TYPES HEE El E PACE 6 HELP SHEET i of 16 FEE Lory Fun Eun OF eturn INDEX COMMAND Se SAMPLE RATE FILTER Low FILTER HIGH COMPRESSOR SANFLE DISPLAY Figure 3 44x PAGE 8 READY x SOUND SAMPLING 14029 HZ SAMPLE LEVEL 2 1 TRIGGER LEVEL E TRIGGER DELAY OF F Soitir T MARIMEA n Sinin NS APRIL 1985 E amp MM COMPUTER MUSICIANS 4 tas _ PACE 8 READY 2 ie en amarae species we have little prior experience gained from our senses that relates visual time domain waveforms to what we LOFA perceive in terms of harmonics or
49. t it was safe to INDEX CLEAR O H TURETE RESET 4 PAGE 4 HARMONIC JERN Along the bottom of the display are the harmonic numbers 1 to 32 A small triangle under the number indicates that the time profile of that harmonic is being displayed on the graph while a cross shows that the profile has a non zero value So what does all this mean Have a look at Figure 2 Two profiles are shown one of which is the First harmonic left to right downwards and the other the Third left to right upwards On receipt of a Compute command the CMI will fill the waveform segments with sound which initially at least has a strong fundamental READY VOICE i HARMS NODE 1 PROFILES ny T pna cna h en COMFUTE SCALE COMMAND XXX PAGE 4 READY xx HARMONIC EN IHF LDIF EN FLOT i ETIE EME aaae ia Atem aagi ASHE eega eSEE B54 72 je a G B E E GEC Em EAE TE FEIET ZERI FUTE CALE INTERP ON ERRANCE S MARCH 1985 E amp MM COMPUTER MUSICIANA sut degenerates into dominant third armonic You don t believe it Look at Figure 3 This is great because with 32 harmonics at our disposal we can create sounds with interesting harmonic structures quickly and easily by selecting harmonics and waving the lightpen in the general direction of the profile area Another bonus is that the profile data is mirrored segment by segment on the Page 5 faders allowing d
50. the most common solution is some sort of noise reduction system such as Dolby In the digital world and as a direct result of research into digital telephony a different solution is to use more binary bits of the byte to represent low signal levels than you use for the high ones This is shown in Figure 5 in which the lower values of the triangle wave use up more of the binary bits than a corresponding increase at large triangle amplitudes The binary data is now no longer linear it s logarithmic For the waveform to be recovered the data must be passed through a DAC that has a curve bent the opposite way to straighten out the sound know all this sounds more thana little involved but it does bring the magic dynamic range ratio up to about 72dB which is at least respectable Only catch is the process only achieves this with a corresponding increase of quantisation noise at larger signal levels though this is masked by the volume of the signal itself You might be familiar with this conver 86 sion process under its commonly used name of companding and it s a system used by many hardware manufacturers including Linn and E mu So if it s so good why doesn t the CMI use it Simple Remember your school days when you added log numbers to multiply Well this is what would happen if the ADD command was used with sounds held in the form generated by Figure 5 instead of adding the sounds together to produce a
51. to a computer based musical instrument Consider a typical case in which a Fairlight user might be playing the music keyboard while listening to a sequence pre recorded on Page 9 Everything is running smoothly the CMI is reading sequence information from the disk sort ing it out and sending the data to the voice channels to be played At the same time the music keyboard is being scanned for pressed notes and more data sent to the channel cards notes are stolen if necessary Next the user may decide to swell a particular voice by moving the appropriate footpedal Here the CMI is forced to deal with an asynchronous event in the normal proceedings so the pedal value has to be updated constantly and the values obtained used to scale the amplitude of the voice throughout its duration And if this were not enough the Fairlight has 17 parameters capable of being controlled in real time It s the unusual multi processor archi tecture of the CMI that enables it to handle so many asynchronous tasks simultaneously but let s move on to the presentation of the controls and their use Page 7 All the controls are handled by Page 7 and a typical display is shown in Figure 1 The page features all the usual controls associated with processing sound each of the eight voices loaded can have its Own unique control setting and can be Saved to disk with a chosen filename and x the suffix CO When a voice is loaded into the
52. tween Well this is where MERGE comes in handy filling in the ZERQed segments and using the segments created on Page 5 as the start and end points OK so far it sounds quite interesting timbrally and looks it too as Figure 13 shows but it s still in need of some amplitude variation An easy way to achieve this is to invert a couple of segments numbers 32 and 96 say and MIX from segments 1 to 32 64 to 32 64 to 96 and 128 to 96 using Page 6 If you NOW CAN COMPOSE LIKE MOZART AND BEETHOVEN LL BE MEGA FAMOUS IN NO TIME LETS SEE WHAT THE PROGRAM DOES WITH THAT PIECE OF AMBIENT MUSIC 1 DIDLAST NIGHT look closely at the differences between Figures 13 and 14 you shouldn t have much difficulty identifying the variation in amplitude especially in the sound s first quarter All that remains is to insert loop points on Page 7 or Page 4 and adjust the attack and damping on Page 7 a O tay PAE GEPRAWP PACKED AER TRUAN Page SPlp GORE
53. uired for a visually coherent display Thus samples that look good will inevitably sound good too Now if all this sounds rather complicated and you re beginning to wonder how anyone gets anywhere near choosing the correct sample rate then take heart It s all in the help pages for Page 8 see Figure 6 A useful sample rate table is included and with a little practice it becomes quite easy to arrive at the correct setting within the space of a few trial samples ADC The actual analogue to digital conversion is accomplished by a 10 bit converter even though the CMI is an eight bit machine Only the top eight bits of the sample values are stored while the two LSBs Least Significant Bits are ignored This improves the linearity of the conversion which means that the signal step size required to cause a conversion value to change by one LSB is fairly constant over the range of the ADC A The relationship between the amplitude o the input signal and the sample values generated is linear When the signal level changes by a given amount irrespective of the absolute value the conversion code always changes by the same amount This is where the Fairlight differs from most other sampling machines such as the Emulator That uses a non linear conversion method called companding which allows more codes to be generated for small signal values than for large ones Whenever a signal is represented by a finite range of numbers
54. xt month page 5 and some revel ations concerning the mysterious Mode a Le NOVEMBER 3984 4 ih i Figure 1 Figure 2 Figure 3 TINDE PAGE 7 READY PUM eee COMMAND EDD2 KOMTROL PARAMETERS CONTROL FILE ERD2 tu MODE 4 BLISSANDG OFF LOOF CNTRL OFF EXP OFF PORTAMENTO OFF LOOP START 1 LEVEL KEYWEL SPEED LOOP UNGTH 1 FILTER 12 CONST TIME ON START SEG 39 DAMPING 268 VIE DEPTH SLUR OFF ATTACK VIE SPEED 6 SUSTAIN OFF on are STICK EASSGT STRMIDI VOICES ERELLOOO TANN GANGSA aia e a a as SULRGHE ell 2s sees 74s SONS ORR ER One F KEYUEL eae QUICK REFERENCE CHART shows ranges and possible pa sach control parameter Control Parameter Range Fatih MORE 1 4 ExF OH OFF 5 SuUTCH1 5 LEVEL w 255 CK EA CHERE TSE FILTER EAE EREL DAMPING E ATTACK cK GLISSANDO PORTAMENTO SPEED C CONSTANT TIME 5 VIBRATO DEFTH Cc ULBRATO SPEED c LOOP CONTROL S LOOP START LOOP LENGTH E START SEGMENT SLUR S E SUSTAIN ON OFF 3 ee vor COMMAND aie CONTROL PARAMETERS CONTROL FILE LOOP co MODE 4 GLISSANDO SWTICHS LOOP CNTRL SWTCHI1 EXF OFF PORTAMENTO OFF LOOP START CNTELL LEVEL KEYVEL SPEED 34 LOOP LNGTH CNTRLe FILTER CONST TIME GN START SEG 1 DAMPING S VIB DEPTH CNTRL3 SLUR SWTCHE ATTACK 1 VIB SPEED 6 SUSTAIN OFF VOICES BASSGT 000 TANN GANGSA ENTRE Y 2 S f oS
55. you of the situation when it occurs by displaying Overflow but is powerless to prevent it happening if the Scale command is issued The only way to recover the sound then is to reload the voice Time now to introduce another concept with which some of you may not be overly familiar Interpolation is the skill of guess ing an unknown value that lies between two known ones and is commonly used to predict values of points on graphs that aren t the actual ones originally plotted When the Interp switch is On each waveform segment is computed from a mix between the harmonic profiles of that segment and those of the next one The difference between the two is subtle and is only really noticeable when the profiles LOHFUTE PACE 4 po a CIDE METERES GS OFF contain rapid changes throughout the duration of the sound Incidentally becoming proficient at using the lightpen for drawing can take a lot of practice so the CMI helps out by providing a Join Plot selector when Join is active any two points struck on the graph are immediately connected by a straight line while fine detail can be drawn by selecting Plot imagine that most of you will be familiar with the Fairlight s Loop function by now so won t go through it all again Suffice to say then that Page 4 offers a quick way of drawing the loop start and length Mode 1 sounds are always calculated so that the waveform fits perfectly into a segment the
56. z oscillator is onboard and this is divided and fed to the individual channel cards It s from this clock that the RAM clocking rates and thus keyboard pitches are generated The whole instrument can be tuned by scaling the master clock Page 2 Commands Looking again at Figure 2 there are several commands at the bottom of the display TRANSFER allows files to be copied from one disk to another using Drive 0 as the destination drive This is essential for creating backup copies of important music and or sounds DELETE erases unwanted files to make room on the disk Invoking this command prompts a confirmation message to prevent ac cidental erasure of important files When a file is deleted FREE SPACE increases by the deleted file size At the very bottom of the display is an example of the QUERY command This tells us that LOCUST IN file will auto matically load eight voices whose names are shown Help Pages By this time you re probably wondering how anybody using a Fairlight ever manages to remember ail the commands especially since we ve only considered Page 2 and there are another 13 still to go The answer is simple Help Pages Figures 4 and 5 show examples of Page 2 Help Pages In fact the entire user s manual is held on the Systems disk and sections relevant to the current display Page can be inspected at any time by typing HELP what else Initially an index sheet is displayed Figure 4
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