Theory of music is a general designation of a complex of disciplines (educational and scientific) of musicology dealing with the theoretical aspects of music.

The most important scientific and educational disciplines: harmony, polyphony, musical form, solfeggio, instrumentology. The theory of music also includes rhythmics (a scientific discipline involved in the study of meter and rhythm), as well as various training courses that do not have a universal (generally recognized) character, for example, “Musical-theoretical systems”. The theoretical provisions on music, presented in a simplified form, are called the elementary theory of music (often abbreviated: ETM)