Programmable current source for filter or oscillator

In order to tune the frequency characteristics of a filter or oscillator as an exponential function of the position of a note on a musical scale, a pulse stream with an exponentially scaled duty cycle is used to gate an on-off switch which controls an electronic tuning signal for the first or second stage of the filter or oscillator. The pulse stream source can be a pulse code generator responsive to a priority note generator, or it can be an oscillator-driven one-shot with an exponentially scaled power supply governing the charging rate of a reactive component which determines the one-shot cycle time. There are also pitch offset and pitch modulation features in the circuit, the latter being usable in a constant deviation or a constant interval mode.