Piano-Tutorial.com

There are other serious faults which hamper pianists, pertaining more to purely technical matters. Such is, for instance, sticking out the thumb, instead of always keeping it ready underneath the palm of the hand in order to facilitate its rapid passage during the changes of position on the keyboard.

This is an important affair, as if this sticking out of the thumb is not checked, it will impede the technical perfection of passage-playing and cause it to be awk- ward, heavy and laboured. Keeping the elbows out is a trick that many fall into, which is both unsightly and detrimental to tone-production, because it forces the hand into unnatural positions, and stiffens the wrists, as well as impairs rapidity and suppleness of execution.