Their music library may be relatively small, and can often frustrate users, but good news! The world from one of the founders, Oleg Fomenko is: mflow are working hard to add tracks:
So if you haven't joined mflow yet I recommend it. You will receive all sorts of tracks in your inbox and earn 20% back off purchases made through your recommendations! And with the library growing all the time one day you may receive flows of Muse in your inbox!