In particular, I was initially thinking about original or mostly original songs based on another work (game, movie, TV show, whatever). Some specific examples:
- Five Nights at Freddy’s - Join Us For a Bite (on YouTube, spooky scary animatronic trigger warning, if that’s not your thing)
- MLP: FIM - Discord (on YouTube)
- Overwatch - No Mercy (on YouTube)
However, this could also probably apply to many other things, like parodies (as mentioned earlier) and maybe Doujin works. I’m not too familiar with doujin, but reading through this thread, it reminds me a little bit of parts of the brony music scene back in the day…
Edit to prevent double-posting: An idea that I thought of that I’m not quite happy with, we could add fanworks to a subseries of the main series (like the one aerozol mentioned). Since the works could maybe be considered a catalogue or collection of similar works. It feels a bit odd to do it this way, but then again, a lot of MusicBrainz is a bit odd…