Square Wave

The square wave contains only odd-numbered harmonics, which gives it a hollow, slightly woody, clarinet-like character distinct from the fuller sawtooth. It is a symmetric special case of the pulse wave, where the signal spends equal time in its high and low states. Because of its odd-harmonic makeup, the square is a favorite for retro video-game tones, punchy basses, and hollow leads. Its most creative feature is pulse-width modulation: by altering how much of each cycle is spent high versus low, you shift the harmonic balance, and when that width is modulated over time it produces a rich, shimmering movement that has become a staple of analog-style pads and strings.