Hey guys,
I’ve successfully hooked up my Game Boy to Renoise via MIDI and sent notes to the Game Boy, fed the sounds it made back into Renoise and processed them there. If you’re interested in how I did it read my writeup over at chipmusic.org for a step by step guide. No soldering required.
Also I’ve played with a few test patterns to show you how it sounds. Listen to my test here
this is pretty cool bro 
I’ve made a new test that I’m comfortable sharing the XRNS of:
http://wolkenspeicherplatz.de/sound/gb_test_3.mp3
http://wolkenspeicherplatz.de/sound/gb_test_3.xrns
Renoise sends MIDI data to the Game Boy, which then produces all the sounds you hear. The sounds get routed back into Renoise in stereo (with the instruments hard panned left and right) where processing on the audio is done in the form of two device chains, using the left and right signal separately to get two instrument groups.
You need a Game Boy with mgb running for this xrns to do anything at all. Connect it to your soundcard’s input to route the audio back through the device chains in the Tracks “Left” and “Right”. You may also have to check if for all 4 instruments the right midi output device is selected, and you may have to adjust the input levels in the tracks labeled “Left” and “Right” depending if your Game Boy is unmodified or prosounded, and at what level your input sound device is set. The first pattern initializes mgb to the right base values for the song to play as intended, don’t skip it.
Feel free to shoot any questions about this my way. Also read the howto at the url from the original post to learn more.
nice just got around to checking this out, and… whoa!
btw nice gameboy remix of those nice arps from 2ndreality =) always loved that part. 