ABSTRACT The author considers the phenomenon of synesthesia, defining it as intersensory association formed by similarity or “contiguity” of heteromodal perceptions. The results of this associative process (occurring mainly at the subconscious level), when coming to the light of consciousness, may be fixed either in verbal form or directly in the sensuous material of the nonverbal arts (most significantly music). Synesthesia calls forth such notions as “melody line,” “the hearing space” and “tone color,” and makes it possible to perceive sounds and chords as “sharp,” “dull” or “high.” Synesthesia (and the particular case of “color hearing”) is the essential component of musical thinking, first of all, in music intended to evoke images.