Sending MIDI to hardware synths
There are plenty of synthesizers and modular synthesizer modules that allow you to send MIDI information like notes and CC messages to control parameters (like control voltage). Depending on the MIDI implementation of your synth or module, you can do a lot!
Check out the code examples for the Volca FM and Volca Sample - the first works on one channel and the second one works on 10 channels. You can start with one of these examples and change MIDI notes, channels and CC messages according to the MIDI implementation of your device.
If you want to do this wirelessly (for example because you’re wearing it), you need two MIDI Madness Makers: one to connect to your synthesizer, the other to wear and to send the touch data to the one connected to the synth. Or you need a long MIDI cable :)
MIDI TRS
Depending on the hardware synth you have, you may need a different MIDI cable. The most common (and current MIDI standard) is Type A. This is also how the MIDI Madness Maker is set up. There is also a type B, which flips the source and sink ([https://minimidi.world/] explains it nicely). This is a little annoying, because it means that you may need a different cable depending on which synth you have, but luckily you don’t need to resolder your MIDI Madness Maker if you want to use a different synth ;).
This is where we buy our MIDI-TRS cables: https://www.thonk.co.uk/shop/befaco-midi-trs-adaptor-cables/ (you can also get them at Thomann).
If you have a synth that uses a TRS input as well, you can use a regular audio cable (or a TRS-TRS MIDI cable if you want to be fancy, like this one). If you have a type B TRS input, you can use a TRS-A/TRS-B dongle which flips the tip and the ring for you (like this one). Alternatively, you can do some hacking on an audio cable by cutting the tip and ring wires, connecting the tip to the ring wire and vice versa (always check with a multimeter if you did it correctly).