harmoniousness vs harmony

harmoniousness and harmony both are nouns.

Word	Noun	Adjective	Verb	Adverb
harmoniousness	Yes	No	No	No
harmony	Yes	No	No	No

As nouns, harmoniousness and harmony are synonyms defined as:

As nouns, harmony is a hypernym of harmoniousness; that is, harmony is a word with a broader meaning than harmoniousness:

harmoniousness (noun)	harmony (noun)
compatibility in opinion and action	an agreeable sound property
the property of sounding harmonious	compatibility in opinion and action
	agreement of opinions
	the structure of music with respect to the composition and progression of chords
	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