Modes of limited transposition

From Wikipedia, the free encyclopedia

The modes of limited transposition are musical modes, which were first compiled by the French composer Olivier Messiaen.

Based on the chromatic scale of twelve notes, these modes are made up of several symmetrical groups, the last note of each group being the first note of the next. After a certain number of chromatic transpositions (i.e. up or down a semitone) each mode cannot be transposed further - the next transposition resulting in exactly the same notes as the first.

For example, the first mode contains notes C, D, E, F#, G#, A#, C; transposing this mode up a semitone gives C#, D#, F, G, A, B, C#. Transposing this up another semitone would give D, E, F#, G#, A#, C, D which is exactly what we started with.

Messiaen found ways of employing all of these modes both harmonically and melodically.

The first mode is divided into six groups of two notes each. It is transposable once. This is the whole-tone scale, quite widespread since Debussy.

The second mode, also called octatonic scale, is divided into four groups of three notes each. It is transposable twice, like the diminished-seventh chord. Here it is, expressed melodically:

The third mode is divided into three groups of four notes each. It is transposable three times, like the augmented triad. Here it is, expressed melodically:

Here are two modes of the fourth type, divided into two groups of five notes each, transposable six times, like the augmented fourth.

The symmetry inherent in these modes (meaning no note can be perceived as the tonic), together with certain rhythmic devices, Messiaen described as containing "the charm of impossibilities."