musical group vs trio

musical group and trio both are nouns.

Word	Noun	Adjective	Verb	Adverb
musical group	Yes	No	No	No
trio	Yes	No	No	No

As nouns, trio is a hyponym of musical group; that is, trio is a word with a more specific, narrower meaning than musical group:

musical group (noun)	trio (noun)
an organization of musicians who perform together	a musical composition for three performers
	three people considered as a unit
	a set of three similar things considered as a unit
	three performers or singers who perform together
	the cardinal number that is the sum of one and one and one