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when you say foam poster board do you mean foam core? like this: http://www.atlantabanners.com/image/cache/data/Pos...I've not tried to peel the paper off of it but I feel like it wouldn't come off evenly and end up ripping out chunks of foam. Can you talk about your method a bit more?
or you could do this if you're not into soldering keyboard contacts: https://www.instructables.com/id/Audio-Typist-Foot-Pedal/
Are you running mobius on a PC? What are you using for midi interface? Can't mobius be controlled from a keyboard? Could you take the guts of a mini usb keyboard, connect the switches to keys and modify your mobius script to use keys instead of midi inputs? That way you don't need a midi interface, arduino or any of the other components related to the connection to the PC. Could use this with the numlock as the mode button and use the numlock light for the record light: https://www.amazon.com/Keyboard-Splaks-Portable-Fi...Also I'm looking to make an all-in-one unit that runs off a raspberry pi running mobius via Wine which apparently is now pretty doable. No schlepping a laptop around.
How to make a prop gun