musical score vs sheet music

musical score and sheet music both are nouns.

Word	Noun	Adjective	Verb	Adverb
musical score	Yes	No	No	No
sheet music	Yes	No	No	No

As nouns, sheet music is a hypernym of musical score; that is, sheet music is a word with a broader meaning than musical score:

musical score: a written form of a musical composition; parts for different instruments appear on separate staves on large pages
sheet music: a musical composition in printed or written form

musical score (noun)	sheet music (noun)
a written form of a musical composition; parts for different instruments appear on separate staves on large pages	a musical composition in printed or written form