serious music vs music genre

serious music and music genre both are nouns.

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

As nouns, music genre is a hypernym of serious music; that is, music 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
music genre: an expressive style of music

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

serious music (noun)	music 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