This variation 13 with its many open strings is an ideal chance to practice placing the new finger while the bow is still on another open string. We practice passages of single notes that cross strings as double stops to ensure that the finger on the new string is ready. This is bar 9.
Practising these passages as double stops also helps develop awareness of finger patterns as well as ensuring that the left hand is balanced. When practising, exaggerate your The movement of the left arm under and around the violin., especially when moving from an open hand position (for the 6th) to a compact hand position (the diminished 5th). In performance we refine this movement of the left arm.
Practicing pizzicato, where we only have one chance to make a clear sound, also encourages confident, fluid finger action. Using a To begin the note the bow grips the string followed by a release during the stroke. Aim for a short sound with lots of resonance. stroke for the double stops is also another good way to build coordination and a clear sound.