To agree in action, adaptation, or effect on the mind; to agree in sense or purport; as, the parts of a mechanism harmonize.

To agree in vocal or musical effect; to form a concord; as, the tones harmonize perfectly.

To adjust in fit proportions; to cause to agree; to show the agreement of; to reconcile the apparent contradiction of.

go together; "The colors don't harmonize"; "Their ideas concorded"

produce a tone which, (often a third or a fifth from the tonic but may also be an octave from the tonic or other seventh or ninth etc.,) is part of the intended cord, or harmony.

To transform a chord by moving each of its tones by a certain number of scale degrees, as determined by the tones of the chord's keyscale. For example, to harmonize a C Major chord in the Keyscale of C Ionian by one step, we move C to D, E to F, and G to A. The resulting D minor chord is the second chord harmony of C Ionian.