(musical synaisthesia as experienced by Olivier Messiaen)

"Mathematics and Group Theory in Music", by Athanase Papadopoulos.

In :- Handbook of Group actions, vol. II (ed. L. Ji; A. Papadopoulos; S.-T. Yau), 32. Higher Education Press and International Press, 2015. pp. 525-572. https://hal.archives-ouvertes.fr/hal-01027418/document

[pagination as per pdf at https://arxiv.org/abs/1407.5757 ]

7.1 (p. 25) "Modes".

"Messiaen’s treatise ... describes ... perception of the relation between mode and color, and fully understanding this requires a certain mental faculty which Messiaen possessed, namely, that of seeing in a precise way the different colors associated with modes, within harmonies or within melodic motives. ... the interested reader can consult [100], p. 95, the chapter entitled Of sounds and colors."

[100] = C. Samuel, Permanences d’Olivier Messiaen (Dialogues et commentaires), Actes Sud, Paris, 1999.

7.2 (p. 26) "Modes of limited transposition".

"Mode 2, ... at his first transposition corresponds to different gradations of blue-violet, which was his favorite color."

7.3 (p. 29) "Modes and colors".

"Messiaen had the rare faculty of having an inner vision of sounds as colors, and mixtures of sounds with mixtures of colors. According to this correspondence, each of the seven modes, at each of its transpositions, has a definite color. Messiaen not only was capable of seeing colors while listening to a piece of music, but also when reading a music score, that is, while hearing mentally the sounds (see [75], Tome 3, p. 79). For instance, Mode 23 (that is, the second mode at its minor-second transposition, which corresponds to the sequence of notes C, D, E♭, F, F♯, A♭, A♮, B), is a “green light foliage with blue, silver and reddish spots”. The colors that he perceived were, like music, changing and moving. Like musical lines, these colors are superimposed and interlaced."

"In his article R. Wagner et Tannh¨auser `a Paris (1861), Baudelaire says that “it would have been very surprising if sound could not suggest color, if color could not give the idea of a melody, etc.”"

[75] = O. Messiaen, Trait´e de rythme, de couleur et d’ornithologie, 7 Tomes, Alphonse Leduc, Paris, 1949–1992.