Coordinating the lift and drop of fingers is an important issue in clarity of articulation, especially when playing chords or double stops.
Practising independence with harmonic touch is useful for focussing on the moment of contact between finger and string. It is also good to help players who tend to press too hard with their left-hand fingers.
Repeat this exercise with normal playing articulation (stopped fingers) and also include 4th finger.
SEE
The Violin & Your Body - Warm Up the Left Hand
Finger Independence - Introduction
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