Metku Mods, a hardware modding site, has an interesting step-by-step photo essay on modding a Casio CTK 530 keyboard.
Why spend hours turning a cheesy Casio keyboard into a control keyboard that only offers limited control? Here’s modder Jani Pönkkö’s reason:
When not modding, I usually compose some music. As an input device for the music software, I use old Casio CTK 530 keyboard. One day I realized how ugly it really is, so it’s time for modding, once again!
Pönkkö spent nothing on the project, using scraps from earlier mod projects, and ended up with an one-of-a-kind, minimal keyboard controller.