on-key vs harmonious

on-key and harmonious both are adjectives.

Word	Noun	Adjective	Verb	Adverb
on-key	No	Yes	No	No
harmonious	No	Yes	No	No

on-key (adjective)	harmonious (adjective)
in tune; accurate in pitch	musically pleasing
	exhibiting equivalence or correspondence among constituents of an entity or between different entities
	existing together in harmony
	suitable and fitting