Notice how we use the elbow to help our Dividing the bowstroke into fractions of the length of the bow.. Every down bow starts at roughly the same place in the bow (around the The place along the bow where the weight is evenly balanced.) and the up bows are leading musically towards the down bows which are on the beat. Using the side of the hair helps further reduce The degree of contact between bowhair and string. on landing.
This stroke is a useful one in several of the variations. Having the upper arm balance the bow as it lands can help with smoothness and control. Much like a plane lands with its back wheels first, let the bow glide on to the string.
This stroke can also help with issues of uneven bow division which occurs in many places in Bach, such as this A bowing pattern of three quavers played 'down, down, up' from Bach’s A minor concerto, 3rd movement. The ‘levering’ of the upper arm on the down bow helps slow down the speed of bow for the 2 notes slurred. Then the drop of the upper arm helps lift the single note so that it does not make an unmusical accent on the weak part of the beat.
When practising, try playing just one phrase, then pause to take time to think before repeating the phrase.