mid-13c., musike, from Old French musique (12c.) and directly from Latin musica "the art of music," also including poetry (also source of Spanish musica, Italian musica, Old High German mosica, German Musik, Dutch muziek, Danish musik), from Greek mousike (techne) "(art) of the Muses," from fem. of mousikos "pertaining to the Muses," from Mousa "Muse" (see muse (n.)). Modern spelling from 1630s. In classical Greece, any art in which the Muses presided, but especially music and lyric poetry.
The use of letters to denote music notes is probably at least as old as ancient Greece, as their numbering system was ill-suited to the job. Natural scales begin at C (not A) because in ancient times the minor mode was more often used than the major one, and the natural minor scale begins at A.
Music box is from 1773, originally "barrel organ;" music hall is from 1842, especially "hall licensed for musical entertainment" (1857). To face the music "accept the consequences" is from 1850; the exact image is uncertain, one theory ties it to stage performers, another to cavalry horses having to be taught to stay calm while the regimental band plays. To make (beautiful) music with someone "have sexual intercourse" is from 1967.