The other day, a colleague asked me about a well-known Bach organ piece, the chorale prelude on the medieval German Christmas carol "In dulci jubilo" from the Orgel-Büchlein, BWV 608:
"What's the current interpretation of Bach's In dulci jubilo in canone all'ottava—the one with quarters in the left hand and 9/8 in the right (3/2 in the pedal)? Can I play the quarters in dotted rhythm, is that a cop-out, or is it considered stylistically correct? My mother played it the other way, and it's a nice challenge, but I'm thinking it's probably out of date."
The colleague asked a bunch of colleagues about this and I think the results will be published in the newsletter of the local chapter of the American Guild of Organists (of which I am, still, a member). But I thought I might put what I wrote here as well. (When playing the piece again the other day I was reminded of some tricky passages and I want to write something about fingerings some time soon—but for now, this is it.) So, here we go.
I don't know what the current interpretation is—that probably depends on the country one lives in, one's teacher, and one's religious views (in matters of performance practice, I mean). To me the question is, What is gained by playing two-against-three? In terms of actual hearing experience, not much, IMHO. In fact, I think a listener in 1715 would have been bewildered by the incomprehensible, "shaky" rhythm and by the de facto strangely arpeggiated chords. It is true that Bach's writing could be unconventional, but he was not an eighteenth-century kind of Stockhausen or Carter.
That two-against-three is hard to play may sound trivial in itself; the real point is not that it's difficult but absurdly difficult in the context of Bach's music (not to mention his contemporaries). In fact, it would make this piece rhythmically the hardest Bach organ piece by far—more so, than, say, the hypercomplex five-part Vater unser from Clavier-Übung III. Bearing in mind that the Orgel-Büchlein was intended (according to Bach's title page) for beginning organists, I simply don't buy that level of complexity. All in all, my best judgement is that it's best to adjust those evenly notated quarters to the triplet movement, taking Bach's hints in mm. 25, 26, 28, 30 (I am aware that one can also use this as evidence to the contrary).
The pedal cantus firmus, BTW, was surely intended to be played an octave lower using a 4-ft. stop; no organ would have had a high F-sharp in Bach's time—in fact, very few European organs do today. The facsimile I have in front of me is to small to see if there's any indication, but I personally think it's quite possible to play the extra tenor voice in the last two measures (dare I call it the quinta vox) in the pedal as well—of course with the same 4-ft. stop and therefore also an octave lower, obviously with the left foot (and yes, I think toe-toe-toe-toe will do fine). Remember that the piece—as almost all of Bach's organ music—was written on two, not three, staves; the separate staff for the pedal is largely a later invention. In any event, the double pedal ending feels very idiomatic to me.