Harmonic rhythm — the rate of chord change — is independent of surface rhythm and shapes perceived energy

Harmonic rhythm is the rate at which chords change, entirely separate from the surface rhythm of individual note events. Fast surface rhythms typically benefit from slow harmonic rhythm (one chord per bar or more) — the harmonic stability gives the listener’s ear an anchor. Slow surface rhythms can accommodate faster harmonic rhythm (one chord per beat), creating more harmonic activity without increasing tempo. Varying the harmonic rhythm is itself a structural technique: slowing it for a bridge creates anticipation; accelerating it at an ending (compressing a 4-bar progression into 2 bars) creates forward drive. Drums and non-pitched instruments do not contribute to harmonic rhythm.

Examples

A busy sixteenth-note synth arpeggio over a single sustained chord for 4 bars = fast surface, slow harmonic rhythm. Slow quarter-note pads with a chord change on every quarter note = slow surface, fast harmonic rhythm.

Assessment

In a current project, identify the harmonic rhythm of each section. Is there variation? Deliberately halve the harmonic rhythm of one section (keep chords twice as long). Does it create contrast? Now double it — does it create drive?