Of the three basic building blocks of any analog synth'"oscillators, filters, and amplifiers'"the oscillator is simple enough to understand: it produces notes with a particular kind of tone color (timbre) as determined by the setting for the oscillator's waveform. This is fed into a filter, usually a low pass filter, which does the job of letting you modify the oscillators 'raw'
Synthesis Survival Guide: Harmonics, Overtones, Partials
It's time to take a journey into the world of synthesis with veteran synthesists, Logic guru and musical maestro, Peter Schwartz! Here he explores harmonics, overtones and partials.