Both words refer to a state of peaceable agreement and coexistence between persons or groups. Harmony suggests an interrelationship in which all elements blend together without social, political, or interpersonal conflict: living together in harmony. Harmony has a metaphorical, evocative feel. Concord, the more formal and less current word, is very similar in meaning, but suggests a more concrete, explicitly political unanimity between parties that have been in competition or conflict. In another, related definition, a concord is a treaty or covenant mutually agreed to by all parties. The resulting concord, in the meaning we’re concerned with here, is grounded in actual agreement and a will to maintain amity.