After writing Doubletalk, I knew the Gameboy had great potential for musicians. Specifically, if a hardware interface could further extend the Gameboy's audio input/output capabilities, the platform offered possibilities as a programmable metronome or alternative instrument.
To further explore this idea, I built a connector to access the Gameboy circuitry using a solderless breadboard. With this connector and breadboard, I successfully interfaced flash memory and an 8-bit Digital to Analog Convertor (DAC) to the Gameboy.
I never quite finished this project. First I got carried away writing C and Assembler code to get the Gameboy to bleep and bloop at me. Then I got distracted by other projects. Now the technology is probably too old to pursue. But it sure looks nice. And it still works, whatever that is worth (maybe the cost of the breadboard?)