The 921 VOLTAGE CONTROLLED OSCILLATOR module features six selectable waveforms (sine, triangle, saw, inverted saw, square and inverted square). These can be adjusted via the Frequency and Range controls to change the tonality of your signal. Finer frequency control is provided via the Scale and Coarse RNG switches. Patch in some control voltages via the two CTRL IN jacks and adjust with the Rectangular Width knob to create some fat Pulse Width Modulation sounds.