Messiaen: Quatre Études de Rythme, with score - II. Mode de valeurs et d'intensités

The second of the four Études de Rythme is the most discussed, as the first work by a European composer to apply numerical organisation to pitch, duration, dynamics, and mode of attack (timbre).
According to the composer's own description, there are separate modes composed of 36 pitches, 24 durations, 12 attacks, and 7 dynamics. The duration scale is separated into three overlapping scales, called "tempi" by the composer, which correspond to the high, middle, and low registers of the piano, and occur in simultaneous superimposition. The first tempo uses 12 chromatic durations applied to the semidemiquaver, the second does the same with the semiquaver unit quaver, and the third with the quaver.
"The durations, intensities and attacks operate on the same plane as the pitches; the combination of modes reveals colors of durations and intensity; each pitch of the same name has a different duration, attack and intensity for each register in which it appears; the influence of register upon the quantitative, phonetic, and dynamic soundscape, and the division into three temporal regions imbues the passage with the spirit of the sounds that traverse them, creating the potential for new variations of colors". (Olivier Messiaen)