Mopidy is an extensible music server written in Python.
Mopidy plays music from local disk, Spotify, SoundCloud, Google Play Music, and more. You edit the playlist from any phone, tablet, or computer using a range of MPD and web clients.
To stream to snapcast you don't have to change anything, but the following code in the mopidy.conf is responsible for the streaming
[audio]
output = audioresample ! audio/x-raw,rate=48000,channels=2,format=S16LE ! audioconvert ! wavenc ! filesink location=/output/snapfifo