05-analysis of interactive technology in thea musgrave`s narcissus
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1. feedback 100 Mod speed 0 1 Hz depth 7 65 msec Feedback ry signal Figure 5 8 The complete digital delay system 12 5 3 3 Control Interface Because variable parameters must be changed during performance an interface of some sort is necessary to control the delay system from the stage Musgrave s directions in the score are so specific to the DIG 411 that any new realization of the work will require some departure from the notation The DIG 411 has back panel inputs for a hold pedal a bypass pedal and a volume pedal On the front panel are knob controls for Input 0 10 Feed Back 10 10 Modulation Speed 0 1 10 Hz and Depth 0 10 Delay Range 2 16 64 128 512 and Time 0 5 2 0 and Delay 0 10 and Dry 0 10 Output levels Additional on off switches control Hi Cut filter Bypass and Hold The Vesta Koza DIG 411 front panel is shown in figure 59 DELAY TIME ouTPuT arrasa i 7 siy yi OG an DIGITAL DELAY i vly Pa 8 nee sly vl gt AE CEES paS S cw Q ae Figure 5 9 Vesta Koza DIG 411 front panel In practice the performer would be required to manipulate knobs 2 feedback 4 modulation depth and 6 time by hand Bypass hold and volume are controlled by two foot switches and a connected to inputs on the back panel of the DIG 411 and a volume pedal2. Many strategies currently exist for cycling through a series of effects changes either by footswitch control or by other means More than likely new strategies will emerge in the near future for controlling parameter changes within an interactive computer music system to which this list of control events should be easily adaptable Musgrave Narcissus performance notes preceding the score Requirements 74 54 SUMMARY The digital delay system required for Narcissus could be easily reconstructed using a wide range of equipment or software based audio processing environments I have based my analysis of the digital delay system and its use in the score on a close examination of the original Vesta Koza DIG 411 system used by Musgrave Therefore I hope that it leads to future performance realizations that are faithful to the intentions of the composer By translating DIG 411 settings into specific parameter values for standard signal processing algorithms I hope to provide enough information to serve as a reliable guide for anyone attempting a recreation of the digital delay system for Narcissus using alternate equipment or technology My own software based realization of the digital delay system is discussed in detail in chapter 9
3. 2000 66 Figure 5 4 Score example delay time modulation Pitch fluctuation of this sort can be achieved by continuously varying modulating the delay time by a small amount similar to a typical flange effect As the delay time shifts audio samples in the delay buffer are played back at a shifting rate of speed As playback speed increases the pitch rises As playback speed decreases the pitch falls This phenomenon is similar to the Doppler effect on pitch from a moving sound source and it should be noted that this pitch shifting effect created by a continuously variable delay only occurs while the delay time is still changing Once the delay time is set the pitch stabilizes at its original pitch level Furthermore the amount of pitch shifting is directly related to the amount of offset from the original delay time and the speed of modulation Larger offsets at faster speeds create more radical pitch shifting effects The score indicates that m odulation speed remains at 0 throughout modulation depth ranges from 0 10 0 3 sic used According to the front panel of the DIG 411 modulation speed is actually scaled from 1 Hz to 10 Hz with a continuous range of settings available between the minimum and maximum settings Therefore the 5 Musgrave Narcissus Although the technical notes indicate modulation values from 0 3 the score contains only modulation settings from 0 to 2 67 modu
4. its basic form it creates a simple echo the input signal is played back after a specified time interval has elapsed This time interval is usually expressed in milliseconds but may range up to several seconds Various manipulations of the delay can produce interesting sonic results some of which are called for in Narcissus Six digital delay parameters must be controlled during performance of this work delay interval time feedback time modulation hold volume and bypass gt Musgrave Narcissus score 61 Delay Time Musgrave indicates three distinct delay times to be applied at various points The DIG 411 delay time was set using two separate knobs The first determined the base delay time labeled range with available settings of 2 8 32 128 and 512 milliseconds The second selected a multiplier of the base delay time with values ranging continuously from 0 5 to 2 labeled time Therefore the base delay time could be set anywhere from one half to double the base delay time Narcissus calls for a base delay time set to 512 milliseconds throughout Multiplier values of 0 5 1 0 and 2 0 are used resulting in 3 separate delay times 256 512 and 1024 milliseconds In Figure 5 2 the delay time is set to 1024 milliseconds 512 x 2 With the sound of the clarinet echoing approximately one second later the first note F is repeated over the E flat which is repeated over the D In this passage feedback see be
5. output is to be controlled by foot pedal Several places in the score call for the delay signal to gradually fade in or out to silence The original setup used a simple analog volume pedal between the delay output and the loudspeaker This technique is used programmatically in Narcissus to illustrate the main character approaching or retreating from the reflecting pool where he sees his own image cautiously approaches the pool J poco HG soz s Meno mosso J 56 Figure 5 6 Score example delay volume Bypass The bypass function is used in Narcissus to turn the entire delay system on or off This feature is used at the opening of the piece so that the unaccompanied introductory section Narcissus wanders through the forest is unaffected by the digital delay Once the bypass is disengaged by foot switch control the delay system is active jo bes a pool of water aceel 5 Delay Ti Saxos A TTT Ag Es l e a soo a TE ona aaa a a D COA PO S Ma A y OO UON S S y a ES tte iA Me Figure 5 7 Score example delay bypass 70 Digital Delay System Summary The digital delay system for Narcissus consists of 1 an audio input source a microphone 2 an echo effect with variable delay time feedback time pitch modulation and functions for delay hold bypass and volume control and 3 audio output via amplifier and loudspeakers The delay effects can be easily d
6. placed between the DIG 411 output and the amplifier Alternate delay systems whether hardware or software based may not feature the same physically accessible controls for the aforementioned variable parameters Aware of this fact at the time the clarinet version was published Musgrave mentions the 73 possibility of using a third footswitch to advance through a sequence of pre set delay settings Such an arrangement allows the performer to easily change delay system parameters while remaining focused on the music The points in the score that require changes to these three parameters are as shown in Table 5 2 Table 5 2 Pre programmable effects changes Score Event Delay time F B Mod 1 m 1 Narcissus wanders through the forest observing 512x05 0 0 2 m 78 Is It Still there 2 3 m 89 Narcissus steps back from the pool 512x 1 4 4 m 172 In the shimmering sunlight 6 5 m 247 Narcissus then responds playfully happily 512x0 5 4 6 m 316 Narcissus anxiously questions 6 7 m 370 The waves surge up Narcissus is drowned 1 8 m 387 All that remains is a distant shimmering vision 2 9 m 398 512x 2 10 m 426 1 11 m 428 The vision disappears the forest is empty 0 Therefore eleven pre programmed delay system changes are required two of which require changes to two parameters simultaneously events 3 and 5
7. scherzo and angular and agitated semi improvised sections The digital delay is more than an effect in this piece Programmatically it assumes the role of Narcissus reflection and at the end the water itself Musically the delay extends the solo instrument in time creating a sonic reflection that very nearly takes on a life of its own Repeating delay effects are used to create harmonies out of a single melodic line and continuous delay time modulation is used to bend the pitch of the delayed sound Duration is listed in the score as 14 minutes but this is variable considering the numerous indications for rubato open ended pauses designed to allow electronic effects to fade before moving on and the variability of the semi improvised segments All electronic sounds are generated in real time directly from the sound of the live clarinet Thea Musgrave Narcissus for Solo Clarinet in Bb with Digital Delay London Novello 1989 59 using the basic features of a digital delay and there are no pre recorded elements Therefore the electronics should be viewed as a flexible extension of the solo clarinet rather than as an accompaniment 5 3 ANALYSIS OF TECHNOLOGY COMPONENTS The electronics required for Narcissus can be broken down into three basic parts a sound reinforcement system microphone amplifier and loudspeakers the digital delay system creating echo effects with several variable parameters and a control in
8. 55 CHAPTER 5 ANALYSIS OF INTERACTIVE TECHNOLOGY IN THEA MUSGRAVE S NARCISSUS FOR CLARINET IN B FLAT AND DIGITAL DELAY My interest in Thea Musgrave s Narcissus began after hearing clarinetist F Gerrard Errante s recording in 1991 4 McGregor Boyle my major advisor at the Peabody computer music studios was the technical director for one of the first performances of Narcissus and had had first hand experience with the original equipment as well as direct supervision from the composer in the concert production Advice from both Boyle and Errante was invaluable in preparing a performance of Narcissus using my own digital delay equipment in April of 2000 The experience of implementing Musgrave s directions using new equipment led me to wonder if the process could be formalized for the benefit of other players A number of performers interested in the piece have expressed their enthusiasm for such an effort as well The result is the following analysis of Musgrave s digital delay system 5 1 HISTORICAL BACKGROUND Narcissus was written in 1987 for flute and digital delay as one of four works resulting from a National Endowment for the Arts Consortium Commissioning Grant The commissioning flutists were Wendy Rolfe Harvey Sollberger Patricia Spencer and Burton Beerman and F Gerrard Errante Electric Clarinet CPS 8607 Brooklyn NY Capstone Records 1991 track 5 56 Robert Willoughby Clarinetis
9. ck at 4 repetitions lasted for 5 seconds 10 repeats Feedback at 2 created 2 5 seconds of echo 5 repeats The same signal was then put through a software based delay with variable feedback also in Max MSP in order to simulate the results of the DIG 411 test The DIG 411 feedback setting of 2 corresponded to a software delay feedback setting of 25 DIG 411 feedback of 4 was equivalent to 50 and the DIG 411 setting of 6 corresponded most closely to 75 feedback in the software simulation It should be noted that on the DIG 411 feedback is not limited to discrete settings The feedback control knob is a potentiometer that allows for settings anywhere along the range between the minimum 0 and maximum 10 values Considering the fact that the performer is required to quickly change these settings manually while handling a flute or clarinet as well it is likely that some variation would occur in performance from the notated values In actual practice with this machine feedback settings of 2 4 and 6 would be rough targets Furthermore differences in microphones 5 A test tone sine wave at 440 Hz was used to first calibrate the DIG 411 input so that the incoming signal would be as close to OdB as possible using the front panel Headroom LED as a guide The same synthesized tone 440 Hz sine wave with an immediate attack and linearly descending decay envelop 1 0 over 500 msec was sent to the DIG 411 input for each of the three f
10. differently Settings above 6 actually produce some very undesirable effects rather than diminishing and fading away the repeated echoes become louder and begin to distort eventually overloading the system Apparently settings above 6 create feedback levels effectively greater than 100 so that even the quietest sounds introduced into the system quickly build into an overwhelming noise It would seem that by limiting the delay settings in Narcissus to 6 and below Musgrave was simply working within the idiomatic boundaries of the equipment on hand rather than choosing settings according to any arbitrary rules a clear demonstration of Musgrave s hands on approach to composition with technology noted by Patricia Spencer in her description of this work and its inspiration The practical question remains using an alternate system what levels of delay feedback would most closely match the DIG 411 settings indicated in the score To Spencer The Musical Shape of Technology 47 64 answer this question I measured the output of the DIG 411 using a test application created with Max MSP software With delay time set to 512 milliseconds 512 x 1 a synthesized test signal was sent to the DIG 411 input and the delay output was recorded into an AIFF sound file for each of the three feedback settings 2 4 and 6 A feedback setting of 6 yielded approximately 18 seconds of diminishing repetitions or 36 repeats With feedba
11. ection in the water that he drowned trying to grasp it Musgrave provides the following program text fragments of which appear throughout the score Narcissus wanders through the forest observing enjoying unselfconscious but self absorbed He sees a pool of water and then as he approaches notices his reflection in the water He is intrigued and then jumps back in fright Once more he approaches it is still there 58 Narcissus steps away from the pool to consider this phenomenon Several times he approaches the figure is always there watching him In the shimmering sunlight Narcissus seems to see this glorious and attractive being moving in the rippling water He is dazzled and slowly holds out his arms To his amazement the figure responds In awe and wonder Narcissus approaches closer and closer With a sudden change of mood Narcissus dances happily and playfully the figure echoing him But then Narcissus begins to question anxiously the lack of any independent response is he being mocked He gets more and more agitated and finally in a fury he rushes headlong into the water to grapple with the figure The waves surge up and Narcissus is drowned There is a distant shimmering vision of Narcissus and his reflection Then in the setting sun the vision disappears the forest is empty and the pool lies undisturbed Narcissus contains a great variety of moods and textures from the unaccompanied opening melody to a playful
12. eedback settings The bell like sound of this test signal enabled easy counting of repetitions 65 and their placement individual playing style and concert hall acoustics will produce slightly different results in actual practice My analysis of the DIG 411 feedback settings as 25 50 and 75 percent of the delay output signal should be used only as an approximate guide for recreation of the digital delay Some variation or adjustment may be necessary to account for real world performance situations Modulation The modulation effect is not clearly defined in the score or in any other published article to date concerning this work According to clarinetist F Gerard Errante who assisted the composer in designing the electronic effects the modulation effect is meant to be a gradual undulating pitch transformation like a slow wide vibrato The modulation effect is applied at the end of the piece as the character of Narcissus drowns in the reflecting pool The waves surge up the figure is shattered amp Narcissus is drowned In Figure 5 4 the modulation effect makes its debut portraying Narcissus watery demise The short delay time in this passage 512 x 0 5 or 256 milliseconds creates a very close mirror of the solo clarinet warped slightly by the oscillating pitch of the delayed signal Delay feedback set to 6 adds thickness to the texture F Gerard Errante email to the author March 9
13. escribed in terms of standard audio signal processing algorithms and the DIG 411 settings given in the score can be translated into specific effect parameters Table 5 1 below summarizes the required effects and their variable parameters as notated in the score and as actual values to be used as a guide for reconstruction with alternate equipment 71 Table 5 1 Delay effect parameters notated and actual values Effect Notated Actual Values Delay Time time interval 512 x 0 5 256 milliseconds between input signal and its 512x 1 512 milliseconds echo 512x 2 1024 milliseconds Feedback amount of delay 0 No feedback 1 repeat output signal routed back to its 2 25 input duration of repeating 4 50 delay 6 75 Modulation Depth slow cyclical 0 No change pitch shifting Speed 0 1 Hz 1 Delay time 7 msec 2 Delay time 21 msec Hold delay loops continuously On Off Feedback 100 Input Off in background allowing ostinato effect Bypass disengages the entire On Off Input Off delay system by cutting input Volume output level from the lt gt Continuous control from 0 to full delay system volume Figure 5 8 shows the complete digital delay system and the signal flow between the various components bypass on off Delay time 2 75 delay Delay p 256 512 1024 msec eee Delay signal trom input output microphone yep original dry signal d Hold bypass on
14. formance to the next The values I have come up with should be used as a guideline only and not as absolute values However I believe that this analysis is precise enough to serve as a guide for future implementations of the modulation effect 68 Hold The hold function allows the performer to capture a short duration of sound in the delay line that loops continually While the hold is engaged no new sounds are added to the delay so the hold loop becomes a background to whatever the performer plays at that time The DIG 411 had a particularly smooth hold feature with no audible clicks or other artifacts creeping in to the sound when the feature is engaged or released Musgrave mentions this requirement as an absolute necessity for any performance implementation of the delay system The hold effect is used quite effectively in Narcissus especially at measure 247 Giocoso Dopio movimento Narcissus then responds playfully happily Figure 5 5 shows delayed arpeggios synchronizing to form brief ostinato chords that accompany the continuing melody in the clarinet The four notes before the hold is engaged B G G F align as a chord since the delay time coincides with the eighth note pulse and they continue to repeat as background accompaniment for the next two and a half measures until the hold is released Figure 5 5 Score example delay hold 5 Musgrave Narcissus score 69 Volume The volume of the delay
15. lation speed setting of zero indicated in the score should be implemented as 0 1 Hz when using other equipment The score indicates depth values of 0 1 and 2 on a scale of 0 10 An analysis of the of the DIG 411 output with an input signal of a sine tone at 440 Hz shows that a modulation setting of 0 causes no pitch deviation a setting of 1 causes a pitch fluctuation between 338 and 442 Hz and a modulation setting of 2 produces a pitch variation from 442 to 258 Hz Using a modulated delay constructed in Max MSP software I was able to produce the same pitch variations as the DIG 411 and record the amount of delay time modulation required to produce such results in terms of variation from the base delay time in milliseconds In other words to produce the 2 Hz pitch variation recorded from a modulation setting of 1 the delay time should be varied by approximately 7 milliseconds in either direction i e delay time continuously fluctuates between 1017 and 1031 milliseconds at a rate of one cycle per 10 seconds 0 1 Hz Fora mod setting of 2 pitch fluctuation between 422 and 458 Hz a delay time modulation of 21 milliseconds is required i e delay time fluctuates gradually between 1003 and 1045 milliseconds One caveat on the Vesta Koza DIG 411 the knob control for modulation depth allows for continuous adjustment between values rather than discrete settings Therefore the exact values for pitch variation may be slightly different from one per
16. low is set to 6 the highest setting in the piece and therefore the F is also heard repeating again but softer over the D operate control qmickl after sound has E a a Figure 5 2 Score example delay time Delay feedback Delay feedback creates a repeating echo by routing a portion of the delay output back to its own input Normally the signal being fed back is at a lower volume than the output and the repeating echoes fade away gradually with a duration 62 that depends on the amount of feedback Musgrave uses this technique very effectively to portray the environment and character of Narcissus Ch the shimmering Sunlight Narcissus seemsto sa eglonous amp Liricameste attractive beng moving in the rippling water Con rm Figure 5 3 Score example delay feedback In the passage shown in Figure 5 3 delay feedback creates a fairly thick texture The shimmering sunlight and rippling water referred to by the program text are expressed in the accelerating and ascending arpeggios which continue to repeat while fading away the Hold feature is explained below Delay feedback is indicated in Narcissus according to settings specific to the DIG 411 values are indicated from 0 to 6 on a scale from 10 to10 Musgrave describes feedback settings as controlling the number of repeats in the delay This should not imply that these re
17. peats are discrete repetitions of a musical phrase or that a feedback setting of 6 will yield six repeats In fact a standard digital delay with variable feedback will route an attenuated portion of the delayed signal usually scaled from 0 Settings between 0 and 10 are not audibly different in any way from settings between 0 and 10 It is not completely clear in the absence of a DIG 411 user manual exactly what the purpose of negative feedback values might be Since negative values are not used in Narcissus I will defer a definitive explanation of this curious feature of the DIG 411 to future research 5 Musgrave Narcissus score 1 63 100 back to the delay inputs The result is that sound repeating in the delay gradually diminishes in volume as less and less of it is fed back each time A feedback setting of 0 will simply produce a single echo of the input signal with no portion of the echo redirected to the delay input The DIG 411 operates on this principle as well so alternate implementations of the delay system should be constructed using scaling factors equivalent to the DIG 411 settings used by the composer The most logical assumption is that the settings from 0 to 10 would correspond to feedback gain from 0 to 100 of the original signal with each number on the dial representing a 10 increment Therefore the maximum setting in the score feedback at 6 would be interpreted as 60 However the DIG 411 behaves quite
18. provide some insights into the composer s intentions as well as recommendations for handling certain common performance problems However Patricia Spencer The Musical Shape of Technology Flutist Quarterly 19 no 3 1994 47 48 FE Gerrard Errante email to the author March 8 2004 57 several key digital delay effects are not explained in general terms but are instead expressed only as DIG 411 knob positions In order to reconstruct the digital delay system using updated or alternate technologies the exact nature of these effects and their parameters must be explicitly understood This information is not contained in the technical notes accompanying the score nor is it to be found in any of the available literature on this work to date The original Vesta Koza DIG 411 Digital Delay used by Musgrave to create this piece has been in the possession of flutist and Narcissus co commissioner Wendy Rolfe Dr Rolfe has very kindly lent me the DIG 411 for this research and I have compared the functions of the original instrument to my own software based reconstruction With this comparison I have analyzed and defined the digital delay system as a set of signal processing algorithms and related parameters rather than as proprietary settings specific to one now obsolete device 5 2 MUSICAL ROLE OF TECHNOLOGY Narcissus is programmatic musically illustrating the Greek myth of Narcissus who was so drawn to his own refl
19. t F Gerrard Errante a noted specialist in music for clarinet and electronics served as technical consultant to Musgrave during the composition of this work In return the composer made a transcription of Narcissus for clarinet Novello Music now publishes both flute and clarinet versions of this work Narcissus requires a digital delay system controlled from the stage by the performer Though relatively simple the electronics are notated for the particular model of digital delay equipment used by the composer a Vesta Koza DIG 411 This instrument is no longer manufactured Even so Narcissus is performed often using alternate equipment Musgrave s technical notes included in the score refer to several other delay devices used by performers who were involved in the creation or early performances of this work However the specificity of the notation for the DIG 411 poses a few problems in reconstructing the digital delay system for those who do not have the benefit of advice from either the composer or the handful of performers who had experience with the original implementation The score includes three pages of technical notes compiled by Musgrave Patricia Spencer Karen Bennet and F Gerard Errante explaining the digital delay system The notes include stage diagrams a sketch of the front and back panels of the DIG 411 and a list of warnings and recommendations for performance setup and preparation These notes are very helpful since they
20. terface foot switches pedals and other devices used to change delay settings during performance The following is an explanation of the required effects the technical methods for implementing them and the musical contexts in which they appear 5 3 1 Sound Reinforcement The sound reinforcement requirements for Narcissus are straightforward and will generally pose no special problems in adapting to available equipment Musgrave suggests a contact microphone to provide audio input from the clarinet to the digital delay system Other microphone systems can work equally well for this piece provided they offer enough isolation from the loudspeakers to prevent signal feedback or other extraneous noise The setup diagram included in the score specifies that the signal output from the digital delay should be routed to a loudspeaker placed stage right while the amplified but 5 Musgrave Narcissus score 60 otherwise unaffected dry clarinet signal should be routed to a second speaker placed stage left This relatively simple arrangement is intended to force an aural separation between the clarinet and its digital reflection input Digital Delay System microphone output left speaker right speaker dry signal delay signal Figure 5 1 Audio system setup 5 3 2 Digital Delay System A digital delay is a standard effect found on most commercially available signal processing equipment In
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