Huddersfield Experimental Laptop Orchestra

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.

Instrumental roles

• 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.

Score

• 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

Performance notes

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 .