Audio: modulation type (0:05)
modulation type plays a modulated melody on alpine bells, also known as tuned cowbells or almglocken. The modulation type figure shows the score:
- Bar 1: a melody starting on the note C in the key of C major.
- Bar 2: modulation from C major to the parallel key of C minor.
- Bar 3: modulation from C minor to the relative key of Eb major.
- Bar 4: modulation from Eb major to the close key of Bb major.
- Bar 5: modulation from Bb major to the distant key of E major.
- Bar 6: return to the note C.
The purpose of modulation is to add contrast to a piece of music, breathe new life into a moribund piece, or to clearly differentiate one section of music from another.
Modulation is a change of key. Since a key has two components, a tonic and a scale, then modulation involves a change of tonic, a change of scale or both together. This determines the type of modulation.
Parallel key modulation keeps the tonic the same and changes the scale. It is the simplest form of modulation and easy to write. The drawback is that some keys may share few notes in common other than the tonic.
All the types of modulation other than parallel key modulation are based on changing the tonic note. The best way to classify them is in terms of the number of notes that two keys share in common. Modulation to a key that shares a lot of notes in common with the current key sounds smoother than modulating to a key with a lot of different notes. This results in three other types of modulation:
- Relative key modulation: both keys share all notes in common.
- Close key modulation: both keys share all but one note in common.
- Distant key modulation: at least two notes differ in both keys.
A few more principles are all that is needed to write modulation:
- How? Abruptly or gradually. An abrupt modulation has an immediate impact and is perfectly feasible. A gradual change may be more desirable and less disturbing to the listener.
- When? In principle, whenever, in practice, commonly at the end of a section.
- For how long? Short-term modulation, called tonicisation, lasts no more than a bar or two, long-term modulation lasts as long as needed.