harmony

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An orderly or pleasing combination of elements in a whole.
• noun A relationship in which various components exist together without destroying one another.
• noun A relationship characterized by a lack of conflict or by agreement, as of opinion or interest.
• noun The study of the structure, progression, and relation of chords.
• noun Simultaneous combination of notes in a chord.
• noun The structure of a work or passage as considered from the point of view of its chordal characteristics and relationships.
• noun A combination of sounds considered pleasing to the ear.
• noun A collation of parallel passages, especially from the Gospels, with a commentary demonstrating their consonance and explaining their discrepancies.

from The Century Dictionary.

• noun A combination of tones that is pleasing to the ear; concord of sounds or tones.
• noun Especially, in music: Music in general, regarded as an agreeable combination of tones.
• noun Any simultaneous combination of consonant or related tones; a concord.
• noun Specifically, a common chord or triad. See triad.
• noun The entire chordal structure of a piece, as distinguished from its melody or its rhythm.
• noun The science of the structure, relations, and practical combination of chords: the fundamental branch of the science of musical composition.
• noun Any arrangement or combination of related parts or elements that is consistent or is esthetically pleasing; agreement of particulars according to some standard of consistency or of the esthetic judgment; an accordant, agreeable, or suitable conjunction or assemblage of details; concord; congruity.
• noun Accord, as in action or feeling; agreement, as in sentiment or interests; concurrence; good understanding; peace and friendship.
• noun A collation of parallel passages from different works treating of the same subject, for the purpose of showing their agreement and of explaining their apparent discrepancies.
• noun In anatomy, same as harmonia, 1.
• noun The tonic, dominant, and subdominant triads of a major key.
• noun Correspondence, consistency, congruity; amity.

from the GNU version of the Collaborative International Dictionary of English.

• noun The just adaptation of parts to each other, in any system or combination of things, or in things intended to form a connected whole; such an agreement between the different parts of a design or composition as to produce unity of effect.
• noun Concord or agreement in facts, opinions, manners, interests, etc.; good correspondence; peace and friendship.
• noun A literary work which brings together or arranges systematically parallel passages of historians respecting the same events, and shows their agreement or consistency.
• noun A succession of chords according to the rules of progression and modulation.
• noun The science which treats of their construction and progression.
• noun (Anat.) See Harmonic suture, under Harmonic.
• noun etc. See under Close, Dispersed, etc.
• noun See Music of the spheres, under Music.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Agreement or accord.
• noun a pleasing combination of elements, or arrangement of sounds
• noun music The academic study of chords.
• noun music Two or more notes played simultaneously to produce a chord.
• noun music The relationship between two distinct musical pitches (musical pitches being frequencies of vibration which produce audible sound) played simultaneously.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun compatibility in opinion and action
• noun a harmonious state of things in general and of their properties (as of colors and sounds); congruity of parts with one another and with the whole
• noun agreement of opinions
• noun an agreeable sound property
• noun the structure of music with respect to the composition and progression of chords