A particular periodic cycling wave, with a particular harmonic content and a particular appearance on an oscilloscope. Several widely used waveforms are generated by the VCOs (or digital equivalent) of synths that use subtractive methods; these are used because their harmonic content reacts well to filtering to produce a variety of useful timbres. They are often named by their visual appearance on a scope screen, and on panel legends, switches or jacks to access different waveforms may be labeled by a drawing or representation of the shape, rather than the name. These commonly used shapes include:
- Pulse wave, which contains large amounts of odd-number harmonics. The harmonic content is easily varied by pulse width modulation.
- Sawtooth wave (also known as the ramp wave), which has a strong second harmonic, with higher harmonics declining in amplitude in an exponential curve. The sawtooth wave is the basic waveform generated by most VCO cores.
- Triangle wave, a waveform containing little of higher-order harmonics. Among other uses, it is better suited to techniques like frequency modulation, which add a lot of harmonic content.
- Sine wave. This one is different because it contains no harmonic content, only a fundamental. It might be used to reinforce the harmonic content of other waveforms, for frequency or amplitude modulation, or for additive synthesis. Filtering a pure sine wave is of no use, since it has no harmonics to filter.