How can we separate pitch from rhythm?

A tune can move upward in pitch while keeping the same rhythm, or repeat one pitch in a lively pattern of long and short notes. Pitch and rhythm describe different parts of what happens. Pitch is how high or low a sound seems; rhythm concerns when sounds begin, how long they last and how silences are arranged.

Two kinds of timing are involved. Within a pitched sound, very rapid repeated vibrations help determine its pitch. Across a musical phrase, notes begin and end on a much slower timescale. Holding a note longer does not by itself make its vibrations repeat faster. Likewise, changing to a higher note need not move its starting time.

The example contains three notes rising from low to middle to high. Their durations are one beat, one beat and two beats: four beats altogether. The final note is both higher and longer, but these are separate properties. A version with all three notes at one pitch could preserve those same durations.

The custom timeline puts relative pitch vertically and duration horizontally, so the two relationships can be seen separately. A wider bar lasts longer; a higher bar represents a higher pitch. The numbers identify notes rather than loudness, and no exact vibration frequencies are supplied. Separating these features explains how musicians can change one part of a phrase while preserving another recognizable pattern.