Here we have the wonderful ZPO from SSF. It has a totally unique take on “thru zero” modulation that couples the frequency modulation with amplitude modulation. Enabling either the linear of exponential FM to go into the thru zero modulation also couples that modulation into the “zero point”. The zero point offers level control in a bipolar fashion which can invert waves and provide ring modulation. Merging TZFM and TZAM alongside the other features such as sync, waveform morphing, 3 types of pulse width modulation, sub oscillators and some unique waveform outputs really elevates this as a powerful analogue oscillator.