A laboratory test instrument, often used in early forms of electronic music including tape studio techniques. A typical function generator can produce many of the same waveforms that are commonly produced by syntheiszer VCOs, such as the sine wave, triangle wave, sawtooth wave, and pulse wave. Some have "symmetry" or "distortion" controls that can produce variations of the shape and therefore the harmonic content of the produced waveforms. Some have the ability to produce "sweeps" in which the frequency is rapidly driven from a low to a high value or vice versa, one time or repeating. Others have the capability to produce special-purpose waveforms which were intended to be used in diagnosis of analog television sets, but for which experimenters found musical applications.
A typical function generator has multiple choices of frequency range, sometimes from under 1 Hz to well into the radio-frequency range, with a vernier that typically can tune the frequency over a 10:1 range. Some have internal modulation oscillators that can be used to produce various forms of vibrato, distortion, or amplitude modulation or frequency modulation effects. (Although, being intended for generation RF radio signals, typically the maximum amount of modulation available is far less than what would be expected in a musical application.) Some function generators have an input for external voltage control, but usually the available range is less than one octave.
Composers using the tape studio techniques often used a function generator to produce their more "electronic sounding" sounds. Typically, the output of the function generator was recorded at a number of different frequencies, and then the performer cut and edited the tape to produce a desired melody or harmony.