Chain Reaction (1991) was written to explore the advantages inherent in the flexibility of MIDI-based electronic instrument controllers, in this case the Airdrums, invented by Pat Downes of Palmtree Instruments.
This instrument consists of two tubes about the size and shape of claves, each of which has six accelerometer-based triggers that respond to motion on three axes. The fundamental difference between these new controller-instruments and traditional acoustic instruments is that now there is no necessary correspondence between a physical gesture and a particular sonic response, which presents particular problems and opportunities for both performers and audience.
Pat built into the operating system for the Airdrums the option of having its output continuously controlled by its input, and this struck me as an experimental idea that I could simply not pass up putting to use.
In each of the six sections of the piece the instrument definition for the Airdrums changes. In the first section it plays a bass line whose pitches are selected just moments before by the MIDI-piano.
In the second section it controls three different sounds: bass, percussion, and an electronic transposition of the saxophone whose transposition interval is also set by the MIDI-piano.
In the third, the bass has disappeared and a long, sampled cymbal-roll coordinates with the piano, while the saxophone transposition has become polyphonic, turning the saxophone into a four-voice chord (still defined by the keyboard).
The fourth section is similar, but now the saxophone itself is controlling the notes of the chord of its own transposition through a pitch-follower.
In the fifth section, the Airdrums turns on and off bursts of electronic sound with each of its twelve triggers, their loudness and presence in the mix providing a rhythmic foil for the improvisations of the other players.
Finally in the last section the Airdrums controls the recirculation of sounds from the other two instruments, and from digital recordings stored in a sampler, through an electronic reverberation system. In this last section, the same gestures that control the electronic sounds have also become conducting cues for the other musicians.
This application of new technology has, I hope, more important reasons than mere novelty: I am experimenting with music in which the musicians cross the boundaries of each other's instrumental territory, where their instruments interact and influence each other directly, and where every player is responsible for a different parameter of the same sound.