serious music vs musical genre

serious music and musical genre both are nouns.

Word	Noun	Adjective	Verb	Adverb
serious music	Yes	No	No	No
musical genre	Yes	No	No	No

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

serious music: traditional genre of music conforming to an established form and appealing to critical interest and developed musical taste
musical genre: an expressive style of music

Other hypernyms of serious music include music genre, musical style.

serious music (noun)	musical genre (noun)
traditional genre of music conforming to an established form and appealing to critical interest and developed musical taste	an expressive style of music