Thumb under and finger over – free course

Five fingers for 88 keys: sooner or later you have to leave the fixed position. The thumb under (the thumb passes beneath the hand) and the finger over (a finger crosses over the thumb) are the two gestures that let you play a continuous line of more than five notes, especially scales. They are also the gestures that most often give away an amateur: a "bump" in the scale, an unwanted accent on the thumb. Let us learn them properly from the outset.

Thumb under (right hand going up)

Play C (1) D (2) E (3). While finger 3 holds E, the thumb is already gliding under the hand towards F. It travels early, without waiting for the last moment.
The thumb plays F; the elbow has moved slightly away from the body and the wrist has slid sideways to the right. The hand follows the thumb; it does not jump.
The hand carries on: G (2), A (3), B (4), C (5).

Finger over (right hand coming down)

In the other direction, from the thumb on F, finger 3 crosses over the thumb to play E. The thumb acts as a pivot and the hand turns slightly around it without the wrist rising.

M:4/4
L:1/8
Q:1/4=60
K:C
!1!C!2!D!3!E!1!F !3!E!1!F!3!E2 | !1!C!2!D!3!E!4!F !1!G!4!F!1!G2 | !1!C!2!D!3!E!1!F !2!G!3!A!4!B!5!c | !5!c!4!B!3!A!2!G !1!F!3!E!2!D!1!C | C8 |]

What about the left hand?

It is the reverse: the left hand passes the thumb under going down and crosses over going up. C scale in the left hand: going up 5 4 3 2 1, then finger 3 crosses over the thumb onto A, 2 on B, 1 on C. Coming down: 1 2 3 on C B A, then the thumb passes under the hand to play G, and 2 3 4 5 on F E D C.

Preparatory exercises (away from the keyboard, then at it)

On a table: rest finger 3 and slide the thumb under the hand and back, twenty times, without the wrist moving up or down.
At the keyboard: finger 3 holds E while the thumb alternates between F and C (C–F–C–F). The thumb must be light and supple.
The scale in fragments: C-D-E-F, then E-F-G (the crossing alone), then the whole scale. Always slowly, listening that the thumb makes no accent.

Common mistakes:

Waiting until the last moment to pass the thumb: the hand then has to "jump", creating a gap and an accent.
Swivelling the wrist like a windscreen wiper or jerking the elbow up: the movement must be sideways and smooth.
Accenting the heavier thumb: consciously lighten it.

Tip: think of the scale as a horizontal movement of the arm, on which the fingers land one after another. The arm leads, the fingers follow.