Resonant Spaces Notes

Andrew McPherson Resonant Spaces for cello and live electronics

Performance Notes

Overview

This piece involves three components: the cello, live electronic processing, and "sequenced" sounds which are predetermined but which render in real time to stay synchronized to the performer. Each component is notated on a separate staff (or pair of staves) in the score.

The cellist needs a bridge contact pickup on his or her instrument. It can be either integrated into the bridge or adhesively attached. A microphone will not work as a substitute, because the live sound plays back over speakers very near to the cello and feedback will inevitably result.

The live sound simulates the sound of a resonating string (and, near the end of the piece, ringing bells). This virtual string is driven using audio from the cello. Depending on the fundamental frequency of the string and the note played by the cello, different pitches are produced and played back by speakers placed near the cellist.

The sequenced sounds are predetermined, but are synchronized to the cellist by means of a series of cue points in the score. At each cue point, the computer pauses and waits for the press of a footswitch to advance. In some cases, several measures go by without any cue points, and it is up to the cellist to stay synchronized to the sequenced sound. An in-ear monitor with a click track is available in these instances to aid in synchronization.

The electronics are designed to be controlled in real-time by the cellist, so no other technician is required in performance. A control box with a footswitch, numeric display, and multi-color LED indicator provides control and visual feedback for the performer. The harmonic series of the string and the cello note lines up at the pitch G4, so this pitch will be produced by the live electronics. # Harmonics of # # "# %# ! # # # # ## # $ string resonator # $ # # "# " # &# $# "# %# Cello spectrum ! &# # &# # # $ &# $ # &# " ! &" &# " % & means 1/6 tone lower than the normal accidental, as in the 7th partial are deviations of 1/4 tone (1/4 sharp, 1/4 flat, and 3/4 flat, respectively), as in the 11th partial. # $ $& ! $ '

! $ ( ( ) ' ' '

Table of pitches produced by different cello notes with the resonating string set to a fundamental of C2. ! Some cello notes produce more than one possible pitch from the resonator, depending on slight variations of intonation. # *# *# *## *# # *# %# # Resonator ! # # # # ! # # # $ # # " # # $ # # # # # # Cello &# %# &# %# # ! # &# %# # *# # # &# %# &# %# # *# ! # *# #&# %# # *#

! $ ' Live Sound and Non-standard Intonation ! ( ) )' )' )' )' )' )' ' The sounds produced by the virtual resonating string are all part of the harmonic series of the string's fundamental pitch. In other words, if the string were tuned to C2 (the open C of the ! cello), it could produce the following pitches:

1. 2. 3. 4. 5. 6. 7. 8. 9. The10. harmonic11. 12. 13. series14. of15. the16. string and the cello # note lines up at# the# pitch%# G4,# etc.so this pitch will ! # # be# produced## # $by the" live electronics. # $ # "# # -14c# -31c -14c -49c -40c -31c # %# # " Harmonics of # # # # # $# " string resonator ! # # # # # $ # # " " The intonation of the harmonic series differs from the conventional even-tempered scale.# &# $While# "# %# most of the above notesCello differ spectrum by only a! few cents (100&# cents = 1 semitone),# &# some# # of$ the more &# $ # &# " "out-of-tune" pitches are labeled above. For the&" most substantially&# detuned notes, different sym- bols are used: ! " % & means 1/6 tone lower than the normal accidental, as in the 7th partial are deviations of 1/4 tone (1/4 sharp, 1/4 flat, and 3/4 flat, respectively), as in the 11th partial. # $ $& ! $ The live sound is not programmed into the computer:' it must be generated by the actions of the cellist. The computer sets only the fundamental pitch of the resonating string; it is up to the performer to select which harmonic sounds. The sounding note arises from the interaction of the ! $ string( fundamental( )and the note played' in the cello. ' '

In the simplestTable case, of pitches the cellist produced plays by difa noteferent in cello the notesharmonic with the series resonating of the string string. set to That a fundamental pitch will of C2. ! be reinforcedSome and cello ring notes strongly produce in themore live than sound. one possible In the pitch more from complex the resonator case,, depending the cellist on plays slight avariations of intonation. note not in the harmonic series. However, since the cello is a timbrally rich source, any note will have its own set of harmonics.*# Wherever*# the harmonic*## series of* the# cello overlaps*# the% #harmonic# # ! # seriesResonator of the! string, that pitch# will be produced.# # For# example, suppose# the string# is tuned to# C2, $ # # " # # $ # and the cellist plays# Eb2: # # # # Cello # &# %# &# %# # ! The harmonic series of the string and the cello # *# # &# %# # *# note lines up at the #pitch*# G4,# & so# this%# &pitch# % #will # be *produced# #&# by%# the live electronics. # # # %# # Harmonics! of ! # # # ## # $ " string resonator # # # $ # # " " # &# $# "# %# Cello spectrum ! &# # &# # # $ &# $ # &# " ! $ &" &# '

! ( ) )!' )' )' )' )' )' ' " % & means 1/6 tone lower than the normal accidental, as in the 7th partial are deviations of 1/4 tone (1/4 sharp, 1/4 flat, and 3/4 flat, respectively), as in the 11th partial. # $ $& ! ' ! $ 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. # etc. # # # $# "# %# ! # # # # # !# $ ( ( ) ' ' # $ #' # " " -14c -31c -14c -49c -40c -31c Table of pitches produced by different cello notes with the resonating string set to a fundamental of C2. ! Some cello notes produce more than one possible pitch from the resonator, depending on slight variations of intonation. # *# *# *## *# # *# %# # Resonator ! # # # # ! # # # $ # # " # # $ # # # # # # Cello &# %# &# %# # ! # &# %# # *# # # &# %# &# %# # *# ! # *# #&# %# # *#

! $ '

! ( ) )' )' )' )' )' )' ' !

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. # etc. # # # $# "# %# ! # # # # # # # $ # # " " -14c -31c -14c -49c -40c -31c The harmonic series of the string and the cello note lines up at the pitch G4, so this pitch will be produced by the live electronics. # %# # Harmonics of # # # # # $# " string resonator ! # # # # # $ # # " " # &# $# "# %# Cello spectrum ! &# # &# # # $ &# $ # &# " ! &" &# " % & means 1/6 tone lower than the normal accidental, as in the 7th partial are deviations of 1/4 tone (1/4 sharp, 1/4 flat, and 3/4 flat, respectively), as in the 11th partial. # $ $& ! $ ' Here is a reference table of the expected results of playing different notes against a string funda- ! $ mental( of (C2. Of course,) with a different' fundamental 'pitch, the whole table' transposes.

Table of pitches produced by different cello notes with the resonating string set to a fundamental of C2. ! Some cello notes produce more than one possible pitch from the resonator, depending on slight variations of intonation. # *# *# *## *# # *# %# # Resonator ! # # # # ! # # # $ # # " # # $ # # # # # # # Cello ! # *# # &# %# &# %# &# %# &# %# # *# # &# %# # *# #&# %# # *# #

The cellist! does not need to concern him- or herself with the precise mechanics of this process, because the pitches notated in the live sound staff already correspond to the notes given in the cello part. In other words, by playing what is written in the cello part, the notated live sound should be the inevitable result. However, the process' is highly sensitive to intonation, so a few! $ cents of pitch variation may be the difference between a very clear tone and a sort of vague re- verberation sound. Since the intonation required deviates from standard even-temperament, ! some( practice) is) required' to) get' all pitches)' to speak)' clearly. (In)' general, )the' higher the' harmonic, the more sensitive to intonation it is.)

! Sequenced Sound and Cue Points

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. The sequenced sounds are notated on the bottom staff of each system. They are rendered by theetc. # # # $# "# %# # computer regardless of what the cellist !plays. # # # # # # # $ # # " " -14c -31c -14c -49c -40c -31c Each cue point is a place that the rendering will pause. When the computer reaches this point, the indicator on the control box will turn green, meaning that it is ready to advance to the next cue point. Tapping the footswitch will advance the rendering.

Cue points are notated in the score as large numbers in square boxes. A small arrow indicates the precise rhythmic location that the footswitch tap should take place. After each footswitch tap, the number shown on the control box display should correspond to the number of that cue. The display is not required for performance, but provides the security of knowing that the computer is in the right place.

The cues can only be advanced when the green light is on, and there is no way to move backwards. If the computer falls behind during performance, the performer should tap as soon as the green light comes on to advance it. If it gets ahead, it will wait at the next cue point for the performer to catch up. In practice, these things rarely present a problem. Certain sections of the score are marked "Follow pulse." These are places where considerable activity takes place in the sequenced sounds, but no cue points are available. In these sections, the cellist must follow the computer by careful listening, by using an in-ear monitor (as described in the setup guide), or by watching the control box display, where the indicator will blink red with each beat, like a metronome.

Control Box

The control box provides a display that looks approximately like this:

Numeric Multi-color display indicator 888

The functions of the indicator and the numeric display are described in the sections above. The control box should be mounted to the stand with a clamp or tape so that the display is clearly legible. The footswitch plugs into the control box, which in turn connects to the computer via MIDI. Andrew McPherson Resonant Spaces for cello and live electronics Setup Guide

Required Equipment

1. Cello with a bridge pickup. Any type of contact pickup will work (e.g. those installed in the bridge or those that attach by adhesive). A microphone will not work, as the live processing involves playback through speakers very near the cello and uncontrollable feedback will result.

2. Mac or PC computer running Csound 5 software. Mac preferred, as all files have been tested on this platform.

3. Audio interface providing at least 1 input channel and 4 output channels. The input channel requires a microphone preamplifier (for the cello pickup), either integrated or external. Exam- ples of suitable audio interfaces: MOTU 828, PreSonus FireBox, etc.

4. MIDI interface with at least one input and one output, for real-time control of electronic sounds. Can be integrated into audio interface (828, FireBox) or external (e.g. M-Audio MIDIs- port USB).

5. Footswitch controller which operates via MIDI. This involves two components: a switch which, when pressed, sends a MIDI signal to the computer, and a numeric display whose value can be set by the computer via MIDI commands. A custom-built controller is available from the composer, or with a few adjustments to the Csound code, a standard MIDI footswitch controller may be able to be substituted (although without the display).

6. Four speakers with suitable amplifiers: two large speakers and two small speakers. Optionally, a subwoofer to augment the large speakers.

7. Optionally, an in-ear monitor for the cellist. Any pair of earbuds with sufficient sound isola- tion will work. The monitor is used to provide timing cues in certain sections of the piece which are not intended to be heard by the audience; however, the same information is provided visually by the custom controller box. Speaker Placement

The two small speakers play live processed sounds from the cello. They should be placed on either side of the cellist, near enough that sounds played through them cannot be differentiated spa- tially from sounds from the cello itself. The speakers should point forward and slightly away from the cellist. In certain situations feedback may result even with the use of a bridge pickup if the speakers are placed too close. Moving them farther away or angling them further outward will help eliminate this problem.

The two large speakers play synthesized material from the computer. They are placed far apart, on opposite sides of the stage, and should actively engage the natural acoustics of the room. In a stage environment, this might mean moving them farther back than normal on the stage. In other environments, it might mean pointing them backwards at the rear wall. The idea is to project a sheet of reflected sound around the room, rather than hearing two distinct point sources.

No special placement is required for a subwoofer, if one is used.

Audio Wiring

This piece uses four output channels. They should be connected as follows:

Channel 1: Both small speakers. In other words, the two small speakers play monophonic material. Channel 2: In-ear monitor for the cellist, if one is used. Otherwise left unconnected. On a MOTU 828, the monitor (a stereo pair of earbuds) can be attached to the headphone monitor port. The left earbud will play channel 1, the right channel 2. Only the right earbud should be used, as the performer should always have one ear free. Channel 3: Large speaker left. Channel 4: Large speaker right.

Reversing left and right in channels 3 and 4 is not a serious issue. If a subwoofer is used, it should be connected to the sum of channels 3 and 4, using a mixer if the subwoofer does not provide this capability internally.

There is one input channel. The cello pickup should be attached to it, via a preamplifier.

Audio Levels

The level of the small speakers should be adjusted so that the live sound is of approximately the same volume as the cello. This will require experimentation, as the live processing will vary in volume depending on the input level of the pickup, the type of pickup, and the specific notes played by the cello. Neither the cello nor the live sound should overly obscure one another. The level of the large speakers should be set to strongly fill the room, but never to be uncom- fortably loud. Much like a cello soloist with an orchestra, the sound from the speakers should never completely cover the sound of the performer.

The input level of the pickup should be determined experimentally, but in general the strategy is the same as adjusting any other input level: as much signal as possible, but never clipping.

Controller Wiring

The controller box should be connected to the MIDI interface via a standard set of two MIDI ca- bles. The box should be attached to the bottom of music stand (with tape or a clamp) so that the performer can read the display clearly. A standard footswitch (i.e. normally open, press to close) is connected to the control box via a 1/8" miniplug. The footswitch should be taped to the floor in a convenient position for the performer.

Files

Csound 5 should be installed and operational on the computer. The following files are used in the performance of this piece: realtime.csd: Contains all the software instruments necessary for performance. score.tab: Read by realtime.csd, contains all specific notes and timings.

The following auxiliary files are available in case modifications need to be made: sequenced.csd: Contains all the same instruments as realtime.csd, and also the notes and timings. Can be played by Csound for testing purposes, but does not wait for footswitch presses as realtime.csd does. audiotest.csd: Tests the MIDI controller and audio by playing pink noise through each succes- sive channel, advanced by pressing the footswitch. stresontest.csd: Used for testing and practicing with the string resonator used to generate the live sound. cscore: A program for MacOS X (Intel) which processes a sorted score from Csound into the tabular format used in score.tab. cscore_custom.c: Source code for the above program, to be linked against the Cscore libraries. midi test: A Max/MSP file which simulates the MIDI controller box. To use this, Csound should be configured to use the virtual MIDI ports provided by Max/MSP. Performance

To start the performance, type at a terminal: csound realtime.csd

The indicator light on the controller box should flash through a variety of colors, and the display should read "888". After a moment the light will turn green and the display will read "0". Tap- ping the footswitch should advance the display to read "1" and trigger the first audio cue. Once it has been verified that this works, stop Csound (control-C), and repeat the above command. When the display reads "0", the performance is ready to begin.

When the performance is finished, stop Csound using control-C.

If any settings for Csound need to be altered, they can be provided at the command line or edited at the top of the realtime.csd file.

(Optional) Making Changes

If any changes need to be made to the instruments, they can be edited in the realtime.csd file. If any changes need to be made to the score, they must be made in sequenced.csd and then a new version of score.tab produced. This is done as follows:

1. Make the desired changes to sequenced.csd. 2. Run the following commands: csound -t0 sequenced.csd ./cscore score.srt > score.tab

The first command does not need to finish (it will play through the whole score), and can be stopped after the first few seconds. It will produce a file called "score.srt" which is used by the cscore program to generate a new version of score.tab.