harmonious

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

• adjective Exhibiting accord in feeling or action.
• adjective Having component elements pleasingly or appropriately combined.
• adjective Characterized by harmony of sound; melodious.

from The Century Dictionary.

• Exhibiting harmony or being in harmony; having parts, forms, relations, or proportions properly accordant each with the others, so that all taken together constitute a consistent or an esthetically pleasing whole; also, being in harmony or concord with something else; congruous.
• Specifically, in music, concordant; consonant; symphonious; agreeable to the ear. See harmony.
• Marked by harmony in action or feeling; acting or living in concord; peaceable; friendly: as, harmonious government; a harmonious family.
• Synonyms Melodious, dulcet, tuneful.
• Amicable, brotherly, neighborly, cordial.

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

• adjective Adapted to each other; having parts proportioned to each other; symmetrical.
• adjective Acting together to a common end; agreeing in action or feeling; living in peace and friendship.
• adjective Vocally or musically concordant; agreeably consonant; symphonious.

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

• adjective Showing accord in feeling or action.
• adjective Having components pleasingly or appropriately combined.
• adjective Melodious; in harmony.

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

• adjective existing together in harmony
• adjective exhibiting equivalence or correspondence among constituents of an entity or between different entities
• adjective suitable and fitting
• adjective musically pleasing