Instructables user Kyle Robinson writes:
The Super gameboy (SGB for short) is Gameboy cartridge player for the Nintendo Entertainment system. Chipmusicians who use LSDJ or Nanoloop can use the SBG to compose on a large screen. Wether its at home with friends, or in a studio environment, the SBG can be a great tool for gameboy composing and today we are going to make it even better.
Check out his how-to for adding an audio line out to the SNES Super Gameboy.