If you want a plain music server, then give Mopidy [0] a try. It is also Open Source [1] and written using Python. I have been using it on my Raspberry Pi and it has been fantastic.
This sounds a lot like Tomahawk: https://tomahawk-player.org/ – playing from different sources and all. Of course that’s a desktop app, but it’s pretty popular already and well designed.
Does it do gapless playback and does it have cuesheet support? I am missing those with mpd/ncmpcpp.