OpenGameArt.org
Dark Solemn Choral with Organ
Credit line
"Dark Solemn Choral with Organ" by ISAo licensed OGA-BY 3.0: https://opengameart.org/content/dark-solemn-choral-with-organ Author's attribution notice: SOUND AIRYLUVS by ISAo https://airyluvs.com/
Where to put it: Game credits or video description. If the entry has a "Copyright/Attribution Notice", follow that.