'Tracking was commissioned by the Danish Radio for the Kronos Quartet and premieredin Copenhagen in October 1990. The computer part was realized at DIEM's studio in Aarhus, Denmark. The electronics are used as an extension of the acoustic instruments. The computer controls both sound treatment of the live musicians as well as a number of synthesizer modules which play digitally altered string sounds as well as completely synthetic material. The digitally altered string sounds were created by recording string instruments and treating these sounds by means of frequency modulation, amplitude modulation, various types of filtering and spectral inversion.

The synthetic sounds were created by means of frequency modulation. Sound treatment of the live instruments includes pitch shifting, reverberation and delay. The amount of treatment and the balance between live instruments and electronic sounds are controlled by a digital mixer (Yamaha DMP7) which in turn is controlled by a computer synchronized with the musicians. The 4 synthesizers and sampler are controlled by the same computer. There are no elements of improvisation in the piece: the live musicians and computer are tightly coordinated and must follow each other closely. (Wayne Siegel)