Here is how you can make a single oscillator sound huge using pulse width modulation at audio rate - using a normal-speed VCO as a mod source rather than a dedicated LFO. Frequency Modulation (FM) synthesis uses the same principle, but modulating the pitch of a waveform at extreme speeds to create additional harmonics, and thus an entirely new sound. Here we are modulating the shape of the wave itself, which also creates additional harmonic content and produces a new and more complex timbre. This process requires a fair amount of experimenting and fine-tuning, but the results can sound massive.

Have a listen to the Black Corporation Kijimi playing 'Everything in Its Right Place' by Radiohead.