Modulation is the process by which a new tonal center is created. There is a bit of a grey area between secondary chord function, tonicization, and modulation. Tonicization tends to be a temporary twisting of the ear toward a tonic, but in a modulation the tonicization is often more well-established by persistent accidentals or through a cadence in the new key.

All modulations can be grouped into one of two categories:

Modulation by Common Chord(s)

The most common way to modulate is through shared chord tones among closely related keys. By moving through one or more common chords, a gradual change is heard. Immediately following the common chords, look for a harmony that is no longer diatonic in the original key. This chord (or chords, in some cases) are referred to as pivot chords. At this point, the music has pivoted into a new tonal center.

Using six-line analysis, one is able to see the path that an excerpt takes through closely related keys.

Steps to six-line analysis:

1. Analyze using lead sheet symbols.
2. Diagram the six closely related keys to the initial tonic underneath the staff.
3. Analyze all possible solutions in all keys.
4. Keeping cadence points in mind, highlight the most appropriate analysis.

Chromatic Modulation

Chromatic modulations are those that do not involve a common chord.