Rhythm in the Presto

Bach manages to create interesting rhythm in a movement containing nothing but sixteenth notes, a perpetual motion. I just want to point out one of these here (and practice referring to uploaded photos of my sheet music).

In the excerpt above, in the section section of the Presto, I think it is ambiguous if the music is meant to be counted as two beats of triplets or three beats of sixteenth-note pairs. In favor of two-beat measures, the first and fourth beats of every other measure (beginning with the second measure shown) repeat the same note. For example, measure 2 counted as two triplets is B23B23. But in favor of three-beat measures, the fifth sixteenth note (beat three) is part of a descending scale, which emphasizes it. Counting measure 2 as three pairs of sixteenths highlights a descending scale: 1D34C6.

This scale is marked lightly in pencil in the music above. Starting in the second measure pictured, the scale goes from D to A and moves from one note to the next on the second and fifth sixteenth notes of every other measures.

For example, in measures 2 through 5, the scale is: 1D34C6;123456;1Bflat34A6;123456.

It's interesting that the scale moves on the second sixteenth note. Emphasizing that note doesn't make sense in three-beat measures or in two-beat measures. Emphasizing the fifth sixteenth note, on the other hand, would emphasize beat three in three-beat measures.

There is a second scale moving at the same time, going from the high B-flat in the second measure shown all the way down to a G on the D-string on the downbeat of the last measure shown.

For example, the second and third measures shown have the following scale: Bflat23Bflat56A23456, G23G23F23456.

This scale occurs on the first and fourth sixteenth notes of measures 2, 4, and 6, and the first sixteenth notes of measures 3, 5, and 7. In measure 8, the first and third sixteenth notes continue the scale. The fifth sixteenth note of measure 8 is an F-sharp instead of the predictable A. That note comes, instead, as the sixth sixteenth note. That in itself creates an interesting little accent. Then the downbeat of measure 9, which one might expect to be a G, is a D instead.

Bach just can't be pegged. That's why his music is so much fun to play and study. Trite but true.

Listen to 1:59 to 2:04 (wow, all that writing about 5 seconds of music!) of Grumiaux's recording to hear the section I am referring to.