Synthesizers work by manipulating electrical signals which appear as sound when they are used to drive audio amplifiers. These tones are generated by electrical circuits which may work by manipulating a signal through a series of oscillators and filters in an analog circuit (as in analog synthesizers), or may perform mathematical manipulation of signals using a microprocessor and digital signal processing (as in digital synthesizers), or by a combination of both methods. Synthesized sounds may sound dramatically different than recordings of natural sounds, though sampling synthesizers significantly blur this distinction.

some sounds that approximate a pure sine wave are whistling, a crystal glass set to vibrate by running a wet finger around its rim, and the sound made by a tuning fork

Examples of non-sinusoidal waveforms include square waves, rectangular waves, ramp waves, triangle waves, spiked waves and sawtooth waves.