religious song vs church music

religious song and church music both are nouns.

Word	Noun	Adjective	Verb	Adverb
religious song	Yes	No	No	No
church music	Yes	No	No	No

As nouns, church music is a hypernym of religious song; that is, church music is a word with a broader meaning than religious song:

religious song: religious music for singing
church music: genre of music composed for performance as part of religious ceremonies

Other hypernyms of religious song include religious music, song, vocal.

religious song (noun)	church music (noun)
religious music for singing	genre of music composed for performance as part of religious ceremonies