Modulate one waveform/track with another (FM synthesis)

Thanks Steve,
This worked - with a sawtooth 37 Hz generated tone as modulator and a long 370 Hz note as modulatee. When I tried a growl (my voice), however, no discernable difference in the modulated signal (also no error message in debug). Any idea why … not strong enough? Wrong frequency ?

Yes, too subtle.
I assume that you had the growl in the lower (right) channel.
Before joining the two mono tracks into a stereo track, Amplify the upper (37 Hz sawtooth) to a peak amplitude of +12 dB (the track must be 32-bit float format as 16-bit / 24-bit tracks can’t go over 0 dB), then join the tracks, then apply the effect.