musical group vs chorus

musical group and chorus both are nouns.

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

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

musical group (noun)	chorus (noun)
an organization of musicians who perform together	the part of a song where a soloist is joined by a group of singers
	any utterance produced simultaneously by a group
	a group of people assembled to sing together
	a body of dancers or singers who perform together
	a company of actors who comment (by speaking or singing in unison) on the action in a classical Greek play

musical group (verb)	chorus (verb)
	utter in unison
	sing in a choir