I am slowly trying to build a MIDI Anglo. I don't have the competence to program an Arduino or RaspberryPi, so I've bought a MIDI interface board.

I looked at Cherry switches but they are too big for the normal button spacing on a concertina, unless you do something complicated with two layers. So I'm using some much smaller switches and hoping they won't feel too different when I come to play it. (They have longer buttons than the one in the picture.)

I reckon I've cracked the push/pull aspect with a strain gauge and some simple electronics instead of bellows. It generates an analogue control voltage proportional (roughly) to the amount of force, and two outputs to enable two sets of relays according to the direction of the force, one for all the push notes and one for all the pull notes. Double-pole switches would be much simpler but I couldn't find any small enough. It will involve an awful lot of wires.