Please Note: This is work in progress and as such circuit diagrams and schematics are for reference only. Do not assume that just because I have up loaded them that they are tested or functional. I can not take any responsibility for any losses incurred as a result of using any information supplied here.
I stared off by getting a second-hand keyboard off of eBay (Oh how I love eBay!) One thing I would recommend if anyone is thinking of doing this, is to take your time choosing your keyboard, don't just go for the first one that you see. I got this one quite cheaply ( I like cheep !) mainly because I new I would need a lot of space inside for my own circuit boards, It also has a large flat surface for all the control knobs and switches I wanted to add.
The first thing I did was to rip-out the internals. I then shortened the keyboard to just two and a half octaves. My intention at the time was to make a valve (tube- if you speak American English) Synth and was going to use thyatrons as the main oscillators, from what I had read and from the schematics I had seen, keyboard tracking was likely to be a problem if the keyboard was any longer than two and a half octaves. By reducing the Keyboard I also gave myself more space for more knobs and switches !
It might also be an idea to make a list of the requirements you will need from your chosen keyboard. I actually made two mistakes when choosing this machine, It didn't even occur to me that the keys might not be velocity sensitive. I also neglected to go for a machine with Pitch and Mod wheels. I did manage to get some DX7 mod and pitch wheels but they are few and far between and not all that cheap, so be warned !