Modulation – moving from one key to another – occurs in many forms of music. In classical music, it is often an important dramatic feature, and is a structural element in certain musical forms (especially sonata and rounded binary form). Like modulation, tonicization implies another key as a tonal center; the difference is that a modulation is confirmed through a cadence in the new key. A key or chord may be tonicized in the middle of a phrase, with no cadence to confirm it as a modulation.
There are two basic methods of modulation: pivot and direct.
- A pivot modulation is found in the middle of a phrase when one harmony or a single pitch is “reinterpreted” to function in each of two keys.
- A direct modulation tends to be found when a new phrase suddenly begins in a new key. There may be one or more turnaround chords (explained below) that soften the transition between keys. Turnarounds are not technically “pivot chords” since they do not occur in the middle of a phrase.