Thanks for the Tomahawk recommendation - it was very nearly what I was looking for.

Unfortunately it does not support the Mac Play/Pause/etc keys. I'm staggered that such an otherwise well put together application lacks such basic functionality.

Support for this was added a couple years ago: https://github.com/tomahawk-player/tomahawk/commit/5cd9e4962...

I think you ought to file a bug, because it's supposed to work.