The QuadVCO module consist of 4 identical voltage controlled oscillators.
It has both 1v/oct and linear frequency modulation inputs and quite a few
output waveforms. There are 2 controls for setting the waveform. The first one
sets the balance between a triangle and a sawwave. The second sets the balance
between the first mix and a pulsewidth modulatable pulse wave. With no input
voltage on the PWM input, the pulse has a duty-cycle of 50%. By different settings
of the 2 contols, different sound spectra can be produced.
A seperate switch is used to change the triangle waveform to a sinus-wave.