KlokSpid MkII - application example: a very basic “FM” operator (but without EG/VCA).
Doing phase modulation (PM) - the phase modulation technique was used by Yamaha for DX synthesizers family.
KlokSpid MkII master frequency is set to 440Hz (visible on second screen capture), output 3 sends unaltered sine waveform (Deform slider set to left position: SINE), output 3 modifier is x1, output 3 voltage amplitude is (default) 10V, output 3 voltage offset is (default) 0V, output 3 amplitude is spread around v-offset (via Bipolar around offset checkbox, checked in this example), by this way, effective output 3 voltage is into -5V/+5V range.
External LFO (by using Surge XT Quad LFO module, here), is set around 150Hz, default sine (undeformed), default bipolar -5V/+5V, from first part of this quad module (green trace on scope). It modulates the output 3 phase (to be more precise, around the phase shift setting), via CV4 input (default bipolar -5V/+5V, visible in top-right vu-meter).
Output 3 is sent directly as audio to studio monitors, via Yamaha/Steinberg UR22C audio interface (ASIO, 48kHz 24-bit WAV, 128 buffer size), then M-Audio BX5 D2 studio monitors.