Funkwhale – Decentralized, self-hosted music server
A word about Clementine, the desktop player: it's powerful, very complete and works well, however it's literally huge, consumes a lot of resources and has some serious memory leaks that if left on for days will either make it eat all system memory, or die without any errors.
This doesn't happen in normal use, it has to be left on for a few days, in fact I'm using it extensively, however it's still really too heavy. I'd be all for a lighter less demanding player.