Psychoacoustic-beats - the intermodulation of frequencies in the brain rather than in air.
To tug at this philosophical thread, this is THE book! Clear prose, that explicates everything between your inner ear and musical enjoyment:
https://www.cambridge.org/core/books/neural-code-of-pitch-and-harmony/F6517CCE7D9F0E728D2689F22216F877#fndtn-information Colour_