OK guys I am wanting to do something similar to what's already been discussed. Basically I have built myself a 4-keyboard (3 manuals and one pedalboard) organ from old 70s analogue organs. There are also 40 tabs (switches). It kind of works as it is but it's nothing great, and the 40 tabs aren't connected to anything at all yet.
So I'm thinking about ignoring the analogue stuff and simply using the keyboards and tabs to generate midi signals, which is not such a big deal I can do keyboard scanning as already discussed, along with debouncing of course, plus I'm capable of reading the midi spec and generating midi protocol - although if I can find a library to do it for me, I don't mind at all!
But I don't really want a midi hardware interface because it's too slow: I want midi over USB. That's the only bit I know nothing about. I suppose I need a library like V-USB but in these forums I've read comments like "Implementing USB within the resource limitations of the these microcontrollers is "non-trivial"", and suggestions that it's best to use a second microcontroller purely for the USB, and that even the V-USB library is still "too complicated". So any pointers greatly welcomed.