I would like a tool that would leverage online repositories of music that is
distributed under liberal licenses (like the Open Music License or the Creative
Commons licenses).  Places like the Open Music Registry
(http://www.openmusicregistry.com) or Magnatune (http://magnatune.com).  These
sites sometimes post RSS feeds of newly submitted music, and I would like to
itegrate these feeds with rhythmbox to automate my discovery of new works.

I envision a mechanism where I can specify "playlists" that refer to one or more
RSS feeds.  Rhythmbox would then periodically update the playlist from those
feeds, download the music, and make them available for play rotation.  The user
should be able to delete unwanted tracks, "blacklist" artists they don't enjoy,
and even "blacklist" music categories.  The unwanted music won't show up in the
play rotation for this playlist, even when new works are available.