Modulation
The moment a song stops visiting another key and moves in. The chords can be identical; what decides it is how long you stay and whether you cadence there. Hear a detour and a move back to back and the difference is obvious in four bars.
- 2 keys
- one pivot chord
- it counts once you cadence
In which styles
- Classical
- Musical theatre
- Pop
- Gospel
- Film music
In short
Modulation works because most keys share chords. A chord that is the IV in your old key might be the I in the new one, and while it sounds your ear has not yet decided which it is. Play a cadence in the new key straight after and the decision is made for it. The pivot chord is the doorway; the cadence is what locks the door behind you.
A lift, or a widening. A modulation resets the listener's frame of reference, which is why a last-chorus key change feels like the song standing up, and why an unprepared one feels like being shoved.
Where it sits in the phrase
Modulations belong at structural joints: into a last chorus, into a bridge, between two halves of a form. Inside a phrase they read as instability rather than as movement, which is occasionally what you want and usually not.
Where you run into this
- A last chorus that jumps up a step and stays there
- A bridge in the relative minor that cadences before it comes back
- A classical exposition that moves to the dominant and makes a point of arriving
The types side by side
The common routes, side by side: to the dominant, the smoothest, because the two keys share six notes. To the relative minor, almost free. To the parallel minor, which changes colour without changing the tonic. Up a half or whole step, the pop modulation, which usually skips the pivot entirely and simply arrives. And the chromatic pivot, where a single altered chord belongs to both keys at once.