I have a DG-20. It was the first of the series, and has no midi. Which is kinda cool cuz you treat it like a real guitar instead of a keyboard.
The tracks on this song have the basic DG-20 beat on it, but there are also many other electronics over it not from the DG-20.
I have been using it a little more of late, always gets the stares and raised eyebrows, but musically it adds nice colour. Trouble is it's a bit awkward as I use the AC instead of batteries, which it munches up by the minute. Also, the weight isn't balanced, it is very heavy on the bottom.
for those who wish to imitate bret, you can indulge here: http://cgi.ebay.com/CASIO-DG-20-MIDI-DIGITAL-GUITAR-PG-MG-SYNTHAXE-RARE_W0QQitemZ270165981696QQihZ017QQcategoryZ2384QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Great ! I recently bought one for 5 euros at a thriftshop and I love it, I offered a guitarist friend to midi-play a riff for my composition. He was horrified with the "instrument" and even tried tuning the strings...
I picked up a DG-1 from a thrift for $2. They probably would have tried to treat it like a more serious instrument, if someone hadn't already apparently tried to modify it. It had bare wire ends hanging out of it and I found lots of little bits of trash paper inside. It wasn't hard to get working again, but I was in for a huge bummer when I discovered that the tuning is controlled by a variable cap/crystal configuration, allowing only about a half step of range regardless of shorting it etc. There went my whammy joystick idea :( While it's great fun sometimes, I've really struggled to figure out how to add just a little bit of expressiveness. I might just rig up some kind of photocell to modulate internal filtering/volume based on hand position etc. and be done with it.
Just bought DG10 at a junk-yard auction today - only 2 strings still connected - others are hanging, having been snapped at the connectors on the bridge - taking off the bridge-plate - you can still pluck the sensors and play the thing like a bass - will try to reconnect the other 4 strings - the sounds are typical early Casio - but I am sure there must be some bend-mods that are possible - a but reluctant to try it withou some more reading ...