serious music vs fugue

serious music and fugue both are nouns.

Word	Noun	Adjective	Verb	Adverb
serious music	Yes	No	No	No
fugue	Yes	No	No	No

As nouns, fugue is a hyponym of serious music; that is, fugue is a word with a more specific, narrower meaning than serious music:

serious music: traditional genre of music conforming to an established form and appealing to critical interest and developed musical taste
fugue: a musical form consisting of a theme repeated a fifth above or a fourth below its first statement

Other hyponyms of serious music include chamber music, opera, cantata, oratorio, concerto, rondeau, rondo.

serious music (noun)	fugue (noun)
traditional genre of music conforming to an established form and appealing to critical interest and developed musical taste	a musical form consisting of a theme repeated a fifth above or a fourth below its first statement
	a dreamlike state of altered consciousness that may last for hours or days
	dissociative disorder in which a person forgets who they are and leaves home to create a new life; during the fugue there is no memory of the former life; after recovering there is no memory for events during the dissociative state