Hi JR,
I (home)-recorded the 2-Part Invention 13 on diatonic. It's at http://www.overblow.com/ludo
Not saying this to tell you how it should be played, but to give you an impression of what you're in for. It's a beautiful piece and fun to practise, but not really easy on diatonic.
My version is 1) out of tune 2) too slow 3) no way near the level I want it to be yet.
I intend to do a better version sometime this summer (haven't had any time for updating/recording).
()() JR "Bulldogge" Ross () () & Snuffy, too:) `----'