This might not be a very exciting project, but it's solved a couple problems for me. I wanted to control a synthesizer from my organ, but I wanted a physical control for pitch bend and modulation, which the organ doesn't have. Also, I can't plug the organ into the synthesizer because the MIDI control change (CC) messages are sent to the synth when I don't want them to be. I can't disable the sending or receiving of MIDI on either instrument. Normally when I play a gig, I would need to bring a second keyboard to control the synth, which is a pain. So I built this little joystick box to give me a physical control and also filter the MIDI messages. My first gig with this setup is tonight and I'm pretty excited!

I used a Teensy 3.2

I'm also considering building another version of this that operates on audio signals, so you could add pitch bend to any keyboard, even vintage, electro-mechanical pianos. I would need a Teensy 3.5 for the FPU and the audio shield. And I would need to implement the phase vocoder technique in order to change the pitch of the signal, but I think I'm at a point where I could tackle this challenge. Besides the hardest part of any project seems to be drilling the holes in the right place!