Aerial Variations (1999)
for solo alto saxophone, chamber orchestra and interactive electronics

"Aerial Variations" is an exploration of interactive electronics in the context of the concerto genre. The traditionally contrasting relationship between soloist (here an alto saxophone) and orchestra is enhanced by the presence of an electronic voice whose activity the soloist directly controls. By means of his own performance gestures, the saxophonist gives rise to the electronic material, which takes flight from the orchestra like another, unseen soloist who soars above the ensemble to form the series of aerial variations alluded to in the title.

The absolute position as well as the velocity and acceleration of the soloist's gestures are captured by an infrared motion device and then immediately analyzed by means of software designed for the piece. The derived gestural data is applied to the control of various digital signal processing methods that take as their source the live saxophone sound, including real-time sampling, harmonization, granular sampling, convolution, and frequency shifting. Other synthesis methods create hybrid timbres from the instruments of the orchestra and the saxophone; the electronic score thus serves as a means to connect the timbral worlds of soloist and orchestra.

Articulated in three broad sections, "Aerial Variations" further plays on the metaphor of flight by making brief reference to the music of two famous birdmen, Olivier Messiaen and Charlie Parker.

Interactive system overview

The interactive electronics deployed in “Aerial Variations” are in part controlled by the gestural movement of the solo alto saxophonist. Gestural information is captured via an infrared motion device and then analyzed by the computer; absolute position as well as velocity and acceleration of the soloist’s gestures are used. The hardware and custom software offer various sensitivity adjustments such that the soloist can use their natural expressive gestures, transforming them through the electronics into a means of controlling the computer interaction and sonic evolution of the piece.

The derived gestural data is applied to the control of various digital signal processing methods, including real-time sampling, harmonization, granular sampling, convolution, frequency shifting, and additive synthesis. In order to gather sonic material for these processes, microphones are placed on the solo saxophone, on the orchestra as a whole, as well as on selected solo instruments within the ensemble. The electronic score thus serves as a means to connect the timbral worlds of soloist and orchestra.