A page with info that I have been able to dig up about the Roland SC-50 Sound Canvas. Apparently, the SC-50 is the same as the SC-55, but without the sounds of the MT32 module. It was released in 1991, it looks like this
Image from http://www.roland.dk/roland/museum/
The SC-55 seems to be much more popular than the SC-50, which means that you can get info on the net more easily. There is a User Group at http://www.grandgent.com/tom/scug/scug.html.
SoundCanvases compared: http://members.home.net/agnew.g/scug/sctypes.html
SC-55 page: http://home5.swipnet.se/~w-55114/index2.htm
e-mail archives http://www.cs.ruu.nl/pub/MIDI/DOC/Sound-Canvas
U Michigan tech sheets by Barton Polot, cached locally
Many sites on the net have links to kafka.uvic.ca, but this site does not have any new information.
Sound canvas SC-50 in depth info
Specs:
Name: SC-55(SC-50,SC-7); SC-155; SCC-1; SCD-10 Brand: Roland Type: MIDI Module (External; Ext. with Sliders; MPU-401 Card; Wave Daughterboard) Poly: 24 Parts: 16 ROM: 3 MB DAC: 16 bit Comp: GM/GS/MT32 see note Instr: 317 Drums: 10 DSP: 2 Extra: note: SC-50 misses MT32 sounds. SC-7 and SCB-10 have less memory (They only have GM)! 7th Guest CD=SC-55+Effects.