chamber music vs serious music

chamber music and serious music both are nouns.

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

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

chamber music: serious music performed by a small group of musicians
serious music: traditional genre of music conforming to an established form and appealing to critical interest and developed musical taste

Other hypernyms of chamber music include classical, classical music.

chamber music (noun)	serious music (noun)
serious music performed by a small group of musicians	traditional genre of music conforming to an established form and appealing to critical interest and developed musical taste