by Samuel Freeman 2008
This piece was composed in response to an invitation from Hewitt to appear with HELO at their first public performance, November 2008.
Comprising four instrumental roles and a score defining how the performance will start and end this is a work that requires players to improvise with the given structures.
- acoustic-instrument one: to play sustained sounds of rich harmonic spectra.
- laptop-instrument one: to perform pitch analysis of ambient sound (microphone input) and modified re-synthesis of detected sinusoidal partials; further details below.
- acoustic-instrument two: percussion to be performed as periods of activity and rest as delimited by onscreen display of laptop-instrument two.
- laptop-instrument two: performed as periods of activity and rest in synchrony with acoustic-instrument two.
- when at rest (not sounding), laptop-instrument two will be sampling audio from the microphone input. This will capture sounds laptop-instrument one players.
- the following period of activity will be, for laptop-instrument two, a re-sounding of the just sampled audio with processing designed to introduce lower frequencies.
- laptop-instrument two will communicate visually its record/playback state with acoustic-player two.
- acoustic-instrument one begins
- laptop-instrument one players enter one at a time
- acoustic- and laptop- instruments two begin - acoustic-instrument one stops
- continue until acoustic-instrument one returns to signal ending
Acoustic-instrument one and laptop-instrument two can be performed by the same player as they do not coincide. The part of laptop-instrument one should be performed by three or more players. The player of acoustic-instrument two should be able to see the screen of laptop-instrument two during the performance. All laptop-instruments each have local audio input and output, such as built-in microphone and small combo-amp.
Laptop-instrument one specification
- the 26 letter keys of the QWERTY-keyboard, plus the Shift modifier keys, form the player interface.
- the length of time each key is held down for is monitored.
- pitch analysis of microphone input will give, for any given moment, a list of five frequency-amplitude pairs which describe the most prominent sinusoidal partials of the input sound.
- when the player presses [Shift]+[letter] the list of partials for that moment will be recorded as associated with that letter key.
- when a letter key is then pressed again, without the Shift modifier key down, the partial list associated with that key will be re-synthesised with relative timing as follows:
- the attack time for the note is equal to the time that the last key press was held for.
- the note will hold for as long as the key is down.
- when the key is released each partial will sustain and then release over a time inversely proportional to the relative amplitude multiplied by the time the key was held for.
- in this way the quieter harmonics are heard for longer than the fundamental (louder) ones
An implementation of this for Max/MSP is available in here .