Are there general rules for playing a three-voice organ piece without pedals?

Question

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.

Answer 1

Definitely no general rules. Adapting three-part organ music for keyboard only is quite radical, as adaptations go, so you'll almost always have to compromise and opportunistically distribute voices just to get by.

That said, there are adaptations of most of Bach's organ music for pianists, see here: https://imslp.org/wiki/Special:ImagefromIndex/745234/qruu. (Of course, that particular adaptation assumes a grand piano and isn't quite suitable for a reed organ, but you can see how it's done.)

Answer 2

In this style of music you shouldn't plan to discard ANYTHING. It's a 3-part texture, we need to hear the three parts. An occasional octave transposition would be acceptable.