Loosely inspired by the Northumbrian Smallpipes using the Hugelton Instruments Digital Compound Oscillator, Digital Dual Traveler, and the Dual Envelope Generator. One oscillator is keyboard driven, with the other three providing a D (D1 voltage), d (D2 voltage), a’ (A2 voltage) drone. The drone oscillator are gated via a VCA driven by the main envelope generator to sound when the keyboard is played. When playing stops a slew limiter is used to keep the drone going for a short period. The drone filters use an LFO each to provide modulation.

Note that the V/Oct range of the oscillators is 0 to 5V. Bogaudio offset modules are used position the voltages accordingly. You may need to set the octave range of your keyboard so that the leftmost bottom C gives -3.0V (i.e. a C1 voltage).