Use Maths ch. 2 to adjust speed and envelope of FM voice. As the voltage rises and falls, the volume of DPO oscillator two adjusts accordingly. Changing the pitch of both oscillators causes timbral & harmonic shifts in the signal.
DPO Oscillator 1 is modulator
DPO Oscillator 2 is carrier
DPO is already hardwired so that Oscillator 1 is already patched into Oscillator 2 and vice versa.
FM explained:
http://www.innovativesynthesis.com/fm-synthesis-made-easy/
AM explained:
https://www.keithmcmillen.com/blog/simple-synthesis-part-9-amplitude-modulation/
DPO Explained:
Maths explained:
FM/AM explained: