Imagination, Visualization, Emotion:
Your sound is your soul. Expose yourself to wonderful violinists so that you may learn what is possible; but — your sound must be uniquely your own voice. What do you hear in your mind’s ear?
All sounds will be a mix of bow speed and weight/pressure. Choose your sounding points:
Nearer the bridge = more tension/resistance = more weight = slower bow speed
Farther from the bridge = less resistance = less weight = faster bow speed
The angle of wood to hair also affects clarity and warmth. Although at the frog the hair should be slightly angled, experiment with flatter hair from the middle of the bow to the tip, especially in concertos.
Find strings that suit your violin.
Think of your hand, arm and entire body as a set of springs. If anything is locked the sound will be stopped, as water by a dam. Keep all joints open. Avoid strain or forcing.
Carve, caress, slide, pour, sink, curve – never hit or strike the violin!
Execute the bow smile. Land in a flattening curve, never with an abrupt vertical descent. (Airplane exercise)
Flexibility in the bow hand and wrist, facilitated by the proper relaxation of the thumb in combination with the proper hand shape, is essential for beauty.
The relation of the fingers of the left hand to the string can affect the sound greatly. Make sure your tips have a feeling of cushion; in lyric playing, play on the pads, not on the bone. The first joint should flex easily. Do not overpress with the fingers or clench with the thumb. The softness in the tips and first joints will especially help sound and intonation in multiple stops.
Vibrato is a key component to your sound and will help loosen your joints.
The arch shape of the fingers can give clarity and focus to your sound. Flattened fingers are fuzzier and warmer.