Octaves, 5ths, and 4ths are stable consonances; 2nds, 7ths, and tritones are tense dissonances that want to move

Intervals between notes form a spectrum from consonant (stable, restful) to dissonant (tense, unstable). Octave, perfect 5th, and perfect 4th are the most consonant: they sound stable and do not create harmonic pressure to move. Major and minor 3rds and 6ths are warm consonances with color. Minor 2nd, major 2nd, minor 7th, major 7th, and tritone (augmented 4th/diminished 5th) are dissonant: they create harmonic tension that resolves when they move to a consonant interval. Tension-to-resolution is the engine of functional harmony and of melody. In live-coding contexts, landing a generated melody on a tension note creates suspense; resolving to a chord tone releases it.

Examples

C–G (perfect 5th) sounds stable; C–F# (tritone) sounds tense. A melody ending on the 7th degree wants to resolve up by half-step to the tonic.

Assessment

Order these intervals from most consonant to most dissonant: major 7th, perfect 5th, minor 2nd, major 3rd, tritone. Explain what ‘wants to move’ means for a dissonant interval.