As the name implies this is a basic VCO with four output waveshapes (pulse, triangle, sine and sawtooth). The core is based on the well known VCO schematics presented in the LM358 datasheet (p. 18). A separate waveshaper circuit produces the rest of the waveforms. The sound of the VCO is lovely buttery smooth and the 4 outputs can be used simultaneously so it can product very nice kick sounds for example.