The first Sonde (1968) produced 200 sine tones that were controlled by individual sliders. (CSTM)

The Sonde (860154), 1968, used twenty electronic sound generators to produce 200 separate pitches, which were turned on and off by mechanical sliders. A second version of the Sonde (910216) was built at the University of Toronto Electronic Music Studio from 1968 to 1970 following Le Caine's design, but this instrument was controlled by a panel of 200 printed circuit keys, each one inch wide. The keys activated sound generators when the conductivity of the performer's finger completed the circuit. The keys were pressure sensitive: when greater force was applied to them, a stronger current was fed to the sound generators.