Muscles of the Hand

The hand contains three sets or muscles:

1. a middle set (interossei ^[1] and lumbricales) ;
2. an external set (thumb muscles) forming the fleshy part of the base of the thumb (the thenar eminence), and
3. an internal set (fifth-finger muscles), forming the hypothenar eminence ^[2].

The middle set is concerned with the actions of the fingers, the other two sets assist in "hollowing" the hand by bringing the thumb and fifth finger closer together. The basic movement of the parts of the hand is that of opposing the thumb to the fingers.
The hand is thus divided fundamentally into two parts, 1) thumb and 2)four fingers.

This division is clearly illustrated in the "grasping" reflex of the infant . Pianistically, in a modified form, it is found in the "passing-underof-the-thumb" in scales and arpeggios. It is quite characteristic of the untrained adult to play bits of pieces by " bunching" the four fingers. This is a further illustration of the physiological division between the fingers and thumb. The next finer division of the hand, separates the four fingers into two groups:

1. the second finger as one, and
2. the third, fourth, and fifth fingers as the second group.

This division is illustrated in the extension of the second finger while the others are flexed. Hence the name "index" finger. The anatomical basis for this separation is found in the accessory tendons (vinculae) which connect the third, fourth, and fifth fingers, but leave the second finger free. The unequal freedom of the third, fourth, and fifth fingers results largely from the fact that the fifth finger action is materially helped by the muscles forming the hypothenar eminence, which reinforces the finger flexion muscles. Whereas the greater freedom of the third finger over the fourth results in part, from its freedom on the second finger side. The fourth finger, on the contrary, is attached on both sides.

In the context of piano playing, the physiological role of the four fingers (excluding the thumb) of each hand is pivotal in tone production, which involves a complex interplay of biomechanics and musical artistry. The division and coordinated action of these fingers contribute significantly to the range, quality, and expressiveness of the sounds produced on the piano.

1. Anatomical Division and Motion Mechanics: Each finger, from the index to the little finger, is anatomically designed for specific movements and roles. The index (second), middle (third), ring (fourth), and little (fifth) fingers have unique lengths, muscle attachments, and joint articulations. These variations contribute to their distinct roles in piano playing. The fingers are primarily controlled by the extrinsic muscles originating in the forearm, as well as intrinsic muscles within the hand.
2. Physiological Role in Tone Production:
   • Index Finger (Second Finger): Often used for melodic articulation and phrasing, the index finger possesses a combination of strength and agility. Its positioning and movement are crucial for dynamic control and initiating trills or grace notes.
   • Middle Finger (Third Finger): Being the longest and typically the strongest, the middle finger contributes significantly to the force and volume of notes. It is central in achieving balanced chord voicing and maintaining legato passages.
   • Ring Finger (Fourth Finger): Historically considered the weakest, the ring finger's strength and independence have been a focus in piano technique development. It plays a vital role in complex chord structures and fast passages, where evenness and control are required.
   • Little Finger (Fifth Finger): Essential for reaching extended intervals and providing leverage at the keyboard's extremes, the little finger often handles the highest notes in chords or melodies, contributing to the overall brightness and expansiveness of sound.
3. Coordination and Control:
   • The fingers must work in a highly coordinated manner, with precise timing and control to ensure fluidity and expressiveness in music.
   • The differential use of finger pressure and speed affects the intensity and timbre of the notes produced. This is crucial for expressing nuances in dynamics and articulation.
   • The alignment of the fingers with the wrist and forearm is essential to prevent injury and to facilitate efficient movement patterns, allowing for sustained performance without fatigue.
4. Contribution to Artistic Expression:
   • Each finger's movement contributes to the overall artistic expression, enabling pianists to convey emotions and stylistic interpretations through their playing.
   • The development of finger independence and control is a fundamental aspect of piano technique, allowing for the execution of complex musical ideas and compositions.

In conclusion, the four fingers of each hand play a distinctive and synergistic role in tone production on the piano. Their precise and coordinated movements, governed by complex muscular and neurological mechanisms, are fundamental to achieving the wide range of expressions and technical demands of piano repertoire. Understanding and mastering these aspects are crucial for pianists to express their musical intentions effectively.

[1]dorsal interossei (DI): In human anatomy, the dorsal interossei (DI) are four muscles in the back of the hand that act to abduct (spread) the index, middle, and ring fingers away from hand's midline (ray of middle finger) and assist in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index, middle and ring fingers.

[2]hypothenar muscles: The hypothenar muscles are a group of three muscles of the palm that control the motion of the little finger.

[3]opponens digiti minimi: The opponens digiti minimi is a muscle in the hand. This muscle is of triangular form, and placed immediately beneath the palmaris brevis, abductor digiti minimi and flexor digiti minimi brevis. It is one of the three hypothenar muscles that control the little finger.