 A waveform generator usually produces a basic geometrical waveform with a fixed or variable timbre and variable pitch.Common waveform generator configurations usually included two or three simple waveforms and often a single pseudo-random-noise generator (PRNG).Available waveforms often included pulse wave (whose timbre can be varied by modifying the duty cycle), square wave (a symmetrical pulse wave producing only odd overtones), triangle wave (which has a fixed timbre containing only odd harmonics, but is softer than a square wave), and sawtooth wave (which has a bright raspy timbre and contains odd and even harmonics).