1475–85; earlier armonise < Middle Frenchharmoniser. See harmony, -ize
Related formshar·mo·niz·a·ble, adjectivehar·mo·ni·za·tion, nounhar·mo·niz·er, nounre·har·mo·nize, verb (used with object),re·har·mo·nized,re·har·mo·niz·ing.un·har·mo·nize, verb (used with object),un·har·mo·nized,un·har·mo·niz·ing.
late 15c., "play or sing in harmony," from French harmoniser (15c.), from Old French harmonie (see harmony). Meaning "be in harmony" is from 1620s; that of "bring into agreement" is from 1727. Related: Harmonized; harmonizing.