Very well documented DMG pitch mod, that I hope will inspire more doomchip. DO IT!

As promised, here is a GetLoFi take on modifying GameBoy DMG-01 with pitch control via the LTC1799 Precision Module from the GetLoFi Shop. The process to replace a fixed 4.19 MHz crystal with a variable digital clock is pretty strait forward, however we will not be responsible for any damage to your hardware, so please do this at your own risk!

via GetLoFi – Gameboy DMG-01 Pitch Modification.