OpenGameArt has a section for music[0], itch.io also has a bunch of free music a...

OpenGameArt has a section for music[0], itch.io also has a bunch of free music assets[1], but do check the license before using them. I use these often and there's some surprisingly great tracks there.

[0]: https://opengameart.org/art-search-advanced?field_art_type_t...

[1]: https://itch.io/game-assets/top-rated/free/tag-music