Stereo Frequency modulation
Put the outer oscillators into ratio and linear fm modes, put the divide controls fully
counter clockwise and the multiply controls at noon or higher so they are at a
significantly higher frequency than the center oscillator. You may want the center
oscillator to be in a pretty low register so this isn’t too painful.
Make sure all modulation controls are fully counter clockwise.
Take the outputs from the outer sine wave outputs, this will give us our nice clean
sine wave fm.
Now (slowly) turn up the FM indexes of the outer oscillators, you should hear a
gradual build up of harmonics.
Next insert a modulator like an LFO or envelope into the FM index inputs.
With very slow modulation on the FM index you should have a deep and ever
changing timbre.
Next try changing the frequency of either the carriers (the outer oscillators) or the
modulator (the inner oscillator). You may find that if the index is high enough the
fundamental is effectively erased and it doesn’t matter very much what frequency the
carriers are as long as they are higher than the modulator, they act more as a filter
for the modulation than independent oscillators.
If you want a little more spice on the sound add some cross phase modulation
between the outer oscillators.
FM INDEX
