Oscillator

An oscillator is a source of repeated motion or a repeating signal. In a synthesizer, it may be an electronic circuit or a calculation in software. At an audible rate, its output supplies the raw material for a musical tone.

Frequency and waveform

Two controls answer different questions. Frequency is how often the cycle repeats: doubling it raises the pitch by an octave. Waveform is the shape of that cycle. An ideal sine wave contains a single frequency. Sawtooth and square waves contain higher harmonics, giving them different colors even at the same fundamental pitch.

Changing waveform is therefore not the same as changing pitch. An oscillator can also be detuned slightly against another, producing beating and a thicker sound.

The rest of the instrument

An oscillator alone does not explain a complete synth patch. Filters shape its spectrum, an envelope can control how its loudness develops, and other signals can move its controls. Some synthesizers combine several oscillators; others use recorded samples or different sound-generation methods.

For a listening exercise, hold one note and switch between sine, square and sawtooth waves at a modest, comparable volume. Listen for the change in brightness while the note name stays the same.