[1.II.2] Finger Positions
Relax the fingers and place your hand on a flat surface with all the fingertips resting on the surface and the wrist at the same height as the knuckles. The hand and fingers should form a dome. All the fingers should be curved. The thumb should point slightly down and bend slightly towards the fingers so that the last (nail) phalange of the thumb is parallel to the other fingers. This slight inward bend of the thumb is useful when playing chords with wide spans. It positions the tip of the thumb parallel to the keys making it less likely to hit adjacent keys. It also orients the thumb so that the correct muscles are used to raise and lower the thumb. The fingers are slightly curled, curving down and meeting the surface at angles near 45 degrees. This curled configuration allows the fingers to play between the black keys. The tip of the thumb and the other fingertips should form an approximate semicircle on the flat surface. If you do this with both hands side by side, the two thumbnails should be facing each other. Use the part of the thumb directly below the thumbnails to play, not the joint between the nail phalange and the middle phalange. The thumb is already too short; therefore, play with its tip for maximum uniformity with all the fingers. For the other fingers, the bone comes close to the skin at the fingertips. At the front pad of the fingertip (opposite the fingernail), the flesh is thicker. This front pad should contact the keys, not the fingertip.
This is just a starting position. Once you begin play, these rules immediately go out the window: you may need to stretch the fingers almost straight, or curl them more, depending on what you are playing. Therefore, although the beginner must learn the ideal curled position, strict adherence to a fixed curled configuration is not correct; this will be discussed in detail later on, especially because the curled position has significant disadvantages.