1. Electronic
An electronic oscillator is an electronic circuit that is capable of creating a repetitive waveform. The most common is a sine wave, but sawtooth, step, square, and triangular waveform oscillators are commonly available. The oscillator circuits are sometimes contained within a device called a signal generator. The signal generator is a box with a variable frequency dial, a waveform selector an attenuator, and a least one pair of output plugs. See diagram on the right.

In musical sound synthesis, oscillators conventionally form the most fundamental synthesis building block. With analog synthesizers, they are realized as electronic oscillators and with digital or software synthesizers they are generated algorithmically. Modern software synthesis environments such as CSound have generalized the oscillator as a type of unit generator (UG), where UGs are primitive modules that produce, modify or acquire audio or control signals.

2. Mechanical

A reciprocating or vibrating mechanical device like a piston or a tuning fork are both mechnical oscillators.

3. Mathematical

In mathematical language an oscillator describes a (continuous) function that varies above and below a mean or other reference level, never fading, never diverging.

In discrete time, this behaviour can be represented as a sequence:

for example the sequence 1, -1, 1, -1, 1, -1,...

not converging to a limit, but remaining bounded.

Geometrically, in continous time, an oscillation follows a path in a bounded (compact) region of space, without settling into ever-smaller regions. In well-behaved cases the path might look like a loop coming back on itself, that is, periodic behaviour; in the worst cases quite irregular movement covering a whole region.

See also: