I've been fixing up an old reed organ, and would love to play some of Bach's organ works on it; for example, I've had my eye on the chorale prelude Wachet auf, ruft uns die Stimme (BWV 645).
The problem is, these pieces were generally written for two hands plus a pedalboard, and this organ doesn't have a pedalboard (you need your feet to pump the bellows).
I know this means I won't be able to play the piece quite as Bach intended it. But there are plenty of keyboard instruments out there that don't have pedalboards. Are there good general rules for adapting a piece from three voices to two like this? Or will it take a good arranger to figure it out on a piece-by-piece or section-by-section basis?
P.S. Here's an excerpt from this particular piece, if it helps. It's marked canto firmo in Tenore, so presumably I shouldn't sacrifice the left hand part.