The SC-50 (SC stands for Sound Canvas) is basically a slimmed down version of the first GM module, the SC-55.
General MIDI is a standard developed primarily by Roland, and now adopted in almost all new synthesizers/keyboards. The General MIDI protocol divides the factory patches in several families.
The sounds contained in this little unit are perhaps surprisingly very good. The basses, piano and vibraphone in particular are quite strong.
Roland SC-50 audio demos in mp3
SC-50 internal Demo Song: Low Flying
PDF Manual at Roland site : www.rolandus.com