Oscillator sync simply synchronizes the period of one waveform with that of another. What does that mean? Basically, the synchronized waveform restarts its wave each time some other waveform completes a cycle.
The naming may differ on some synthesizers, but typically there is a “master” oscillator (often OSC 1) which controls the cycles of the “slave” oscillator (often OSC 2). In order for oscillator sync to have any kind of audible effect, the slave oscillator must be tuned higher than the master. And, it must not be tuned to octave multiples of the master.
Listen to the podcast for examples of what it sounds like.
Fred Welsh’s book, Synthesizer Cookbook: Synthesizer Programming, Sound Analysis, and Universal Patch Book, is an excellent reference on using oscillator sync to produce sounds that couldn’t otherwise be achieved.
Looking for the ESQ-1 example patch we created near the end of the episode? Here it is: oscillator sync example for Ensoniq ESQ-1.