"Genius does many things by instinct. And it sometimes happens that very
great performers, trying to explain some technical function, do not know
how to make their meaning clear. With regard to bowing, I remember that
Joachim (a master colorist with the bow) used to tell his students to
play largely with the wrist. What he really meant was with an
elbow-joint movement, that is, moving the bow, which should always be
connected with a movement of the forearm by means of the elbow-joint.
The ideal bow stroke results from keeping the joints of the right arm
loose, and at the same time firm enough to control each motion made. A
difficult thing for the student is to learn to draw the bow across the
strings _at a right angle_, the only way to produce a good tone. I find
it helps my pupils to tell them not to think of the position of the
bow-arm while drawing the bow across the strings, but merely to follow
with the tips of the fingers of the right hand an imaginary line running
at a right angle across the strings. The whole bow then moves as it
should, and the arm motions unconsciously adjust themselves.