I’ve been playing around with the Tomahawk Social Media Player desktop app for about a week now - since brother Markus introduced me to it - it exists in both PC and Mac flavours, with the latter being slightly more seamless an experience at the moment. This is definitely NOT a replacement for Spotify, more of a useful addition to it - as the largest library of quality music media comes from Spotify itself (requires Premium account).
Out of the box, Tomahawk does not do much more than play...