oratorio vs serious music

oratorio and serious music both are nouns.

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

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

oratorio: a musical composition for voices and orchestra based on a religious text
serious music: traditional genre of music conforming to an established form and appealing to critical interest and developed musical taste

Other hypernyms of oratorio include classical, classical music.

oratorio (noun)	serious music (noun)
a musical composition for voices and orchestra based on a religious text	traditional genre of music conforming to an established form and appealing to critical interest and developed musical taste