A sequential voltage source steps through programmed voltages, driving pitch, amplitude and duration at once

The Buchla Model 123/146 Sequential Voltage Source is a hardware step sequencer predating digital sequencers. It emits a sequence of programmed control voltages — 2–8 steps on the 123, 2–16 on the 146 — at each of three simultaneous outputs, advancing one step per incoming trigger pulse (usually from a timing-pulse generator). Because the three channels are independent, one pass can program pitch on one output, amplitude on a second, and duration on a third for the same steps, building compound melodic-rhythmic phrases from a single module. Its output is control voltage, so it can drive a VCO’s pitch, a VCA’s level, and a pulse generator’s rate simultaneously — the ancestor of the modern step sequencer.

Examples

Model 123: ‘Produces a sequence of two to eight programmed voltages at each of three outputs. Switching is accomplished by applying a pulse.’ ‘Unit may be used to simultaneously program pitch, amplitude, and duration.‘

Assessment

Explain how a step sequencer advances and what its three simultaneous outputs let you program in one pass that a single-channel sequencer cannot.