The New Grove Dictionary Of Music And Musicians (Second Edition) defines music theory as:
...principally the study of the structure of music. This can be divided into melody, rhythm, counterpoint, harmony and form, but these elements are difficult to distinguish from each other and to separate from their contexts. At a more fundamental level theory includes consideration of tonal systems, scales, tuning, intervals, consonance, dissonance, durational proportions and the acoustics of pitch systems. A body of theory exists also about other aspects of music, such as composition, performance, orchestration, ornamentation, improvisation and electronic sound production.
