This must be the day of Kickstarter projects. This project turns an original Gameboy into a unique music instrument complete with analog controls and a stereo/mono switch. While this may be of use only to hard core knob twiddlers, but for $174 you can get a fully modded Gameboy and 6 volt power supply so you and your band can add some boops and beeps to your latest song.
The kit actually “improves” the Gameboy audio, adding controls for Cutoff, Resonance, Bypass, Envelope Follower. This is obviously some hardcore chiptune action so I won’t pretend to explain it. Here is how the creator describes it:
The filter can operate in mono mode, effecting the entire signal from the Gameboy. In stereo mode, the clean signal from the Gameboy is panned hard left, while the filtered signal is panned hard right. This allows the performer to selectively program what elements of their audio will pass through the filter.
The Envelope Follower allows the filter to be automatically animated by the dynamics of the signal. This is particularly useful for imparting filter characteristics to resonant basslines.
You can have the creators mod your own Gameboy for $160 and buy the kit for $90.