Practising with a mirror is extremely useful – for both hands. However, one must not become too self-obsessed. When practising with a mirror, try to position yourself so you do not see your own face. You will gain much in the way of objectivity
Play a slow scale, watching the small part of the string between the bridge and the bow hair. Each time you draw the bow, you will see the string push to the left (for up bow) or the right (for down bow). Do your best to maintain this angle in the string as you play, […]
It may be that you have never seen a string move. It doesn’t do what you think. This video will begin to change the way you think about sound production. Many thanks to whoever made it. And here is another nice explanation.
Play long slow notes with a gradual decrescendo. The first impulse from the bow starts its energy. The the motion of the bow afterward defines how its resonance continues. Skate with the bow: glide powerfully from the strength of the first impulse.
The energy of the string has an outlet at the bridge. Watch the bridge drink the string motion (audio in). Feel the instrument’s resonance as you play (audio out). The invisible motion of the bridge becomes the sound of the instrument.
Experiment with the distance of the bow from the bridge. Create softness and distance over the fingerboard; create brightness and proximity near the bridge. Make the greatest possible differences in timbre and dynamics. Find the borders of string and instrument.
Play a scale or arpeggio. Use the energy of motion in the string to connect the left and right hands. Between your hands you hold the energy that becomes the sound.
Play a scale or arpeggio. As you play, change bow speeds from very slow to very fast. Create large changes in the size (amplitude) of the visible vibration of the string and listen for the changes in dynamic.
Play a scale slowly, combining two exercieses: Think clearly of each pitch before playing. After the string length is set, pour energy smoothly into it with the bow.
Play a scale slowly. Watch the energy of the bow create a parallel (sideways) vibration in the string. Keep bow pressure fairly light. A taut string contains energy: release it.