there are a few projects I've seen that I might be able to scale down for this, but thought I would just ask if anyone knows any good resources...
I have a few teensy/arduino synths that are currently controlled by sending note/CC data via MIDI.
Ideally I'd like to develop these so that most of the CC controls can be changed by physical pots/switches on the case, whilst still being able to send MIDI to the synth via the MIDI port (especially note/pitch bend from a keyboard) (so I guess this will involve adding some kind of "MIDI merge" as well?)
I found this, which feels like it may be a good starting point, but I wondered if there are any potential pitfalls or anyone has any useful experience to share in this area?
Did I get it right? You want to use a keyboard to send MIDI to a synth. And you want your own pots and gadgets, which will add control to the same synth. Making your own gadgets using Arduino, pots and whatnot is pretty straight forward. Having another midi controller as well and merging everything requires "MIDI through" technique. Your keyboard might have MIDI out, MIDI in and MIDI through. If it's old school, you have three 5 pin DIN contacts for that. Connect your own gadget to MIDI through and MIDI out to the synth. Your keyboard will do the merging. If it doesn't have the MIDI through, you might still be lucky and whatever goes to MIDI in, goes also out from MIDI out. Might need settings.
You can also build your own gadget so that it has a MIDI in and MIDI out.Then you can connect your keyboard to your gadget and your gadget to the synth. Then you are responsible for programming it to handle the merging. Last time I checked, internet had advice on how to do this.