But the Sixth Partita, well, that's an entirely different kettle of fish. This is a particularly recondite gigue cast as a fugue with a chromatic leaping subject and the second half uses the same subject in inversion. But the time signature! It's like two "cut" time signatures facing one another, or like a circle with a slash. Like this, but with the slash vertical, not at an angle: ∅ What could this possibly mean? Not too surprisingly it is also derived from Medieval metric notation. The circle with a vertical slash stands for proportio dupla sometimes called diminutio simplex. From the 14th to the 16th centuries this meant that the correct rhythmic reading of the notes would be two short notes making up a long, as opposed to three short notes making up a long. It seems as if Bach is using a very, very old-fashioned metric signature to tell the player that, yes, this is a gigue all right, but it is a gigue in duple time! Very odd, since gigues are, as I said, always with a triple subdivision. Just not this one. It still sounds, oddly, like a gigue ... in duple time. How strange that Bach would choose to end, not just the set of six partitas, but the very lifespan of the Baroque keyboard suite itself, with such an unusual movement.
For an entirely different reading of this whole time signature issue, have a look at this essay which relies more on how this kind of signature was interpreted in the 17th and 18th centuries.
Now, for a couple of performances. The first is by Murray Perahia and he plays the rhythms as they appear in the score.
The next is Trevor Pinnock interpreting the rhythms as indicating triplets in the way suggested in the essay I just linked to. Of course doing this involves quite a lot of tinkering! How much tinkering, you ask? Well this chart from the essay illustrates one scholar's suggestions. On the left is the original time signature and rhythms. UPDATE (correcting left to right): On the right is the proposed "tripletization" with a 24/8 time signature and the rhythms adapted appropriately:
Now let's have a listen to what that sounds like:
Which do you prefer? I lean towards the duple version because I think it is more interesting of Bach to have written a truly duple gigue than that he wrote one that looks like a duple gigue, but one you can, with a lot of tinkering, turn into a triple gigue. On the other hand, isn't it even more fascinating that both of these possibilities exist?