Is it farther or further?
"related notes in music," 1590s, ultimately a shortening of accord (or borrowed from a similar development in French) and influenced by Latin chorda "catgut, a string" of a musical instrument (see cord (n.)). Spelling with an -h- first recorded c.1600, from confusion with chord (n.2). Originally two notes; of three or more from 18c.
Variant of cord.
In music, the sound of three or more notes played at the same time. The history of Western music is marked by an increase in complexity of the chords composers use.