I’ve always been fascinated by bass pedals. No idea why, but the thought of being able to play a low pedal tone while I play over the top just intrigues me. Since the DMC boards can read a whole bunch of switches and then send out MIDI, it seemed like a natural fit. Connect the MIDI port to a synth or a laptop and you’ve got a set of faux-Taurus pedals for a fraction of the cost of the real thing.
I found a junked organ and removed the bass pedals. Each pedal has its own switch and its own wire, and there’s a common wire. On the original organ, closing a switch to the common triggers a bass tone. The original design of the organ pedals gives “low note priority,” so the common contact is run in series to each switch. When a lower pedal is pressed, the common to the upper switches is opened, and only the lowest pressed pedal makes contact. Wiring all the switch common contacts together makes the pedals polyphonic when connected to the DMC.
The implementation is simple: Wire one switch contact to each terminal of the DMC, and the common wire goes to ground. That’s it.
The firmware is super-simple. Watch a switch, and if the switch is pressed, send the MIDI note on for that note. If the switch is released, send MIDI note off for that same note. Repeat for the other twelve switches.
Future mods include transpose and octave shift buttons – press the transpose button, then step on the key you’d like to serve as the root note. Octave switching works the same way, but I think I might use two buttons to shift up and down quickly. I’ll probably also put a 1/4″ jack for an expression pedal to control the MIDI volume.