In the preface to La Nativité du Seigneur, and later in Technique, Messiaen describes and tabulates seven ‘modes of limited transposition’. These are pitch-class collections with properties of internal organisation that restrict the number of distinct transpositional levels of each collection to significantly fewer than the twelve that are available to most other collections, including the diatonic major scale.

Each collection is itself generated by successive transpositions of a small cell of a few notes, giving a characteristic repertoire of melodic configurations, and each with the exception of modes 1 and 5 also contains a number of triads and/or other harmonies familiar from tonal music, something which Messiaen was able to exploit musically. The regular internal structure of the modes means that where one such harmony is found, others will be found at regular intervals from it, allowing the composer ‘[either] to give predominance to one of the tonalities or to leave the tonal impression unsettled’. For example, the form of mode 2 which contains the C major triad also includes the E♭ major, F# major and A major triads. The tonal focus might settle for a while on any one of these, or they might be cycled in quick succession.

Mode 1

This mode, known elsewhere as the whole-tone scale, is entirely regular in construction, being generated by the six-fold transposition of a single note at successive intervals of two semitones (ic2).