The four moves

The vocabulary of the hand.

Start from the natural position: one finger per key, so 1-2-3 sit on C-D-E. Then compare every pair of fingers with that.

The rule. For fingers a and b the natural distance is b − a keys. Fewer keys: contraction. More keys: extension. Equal: natural. If the fingers are not neighbours and the distance is natural, it is a jump; if they are neighbours, a fill.

Extension

Changes the position of the hand

Extension

Fingers reach farther than natural. The hand opens.

For example: 1 on C, 2 on E: farther apart than 1-2 would be naturally (C-D).

Contraction

Changes the position of the hand

Contraction

Fingers come closer than natural. The hand closes.

For example: 1-3 on C-D instead of C-E: closer than natural, so the hand closes.

Jump

Keeps the position of the hand

Jump

Fingers skip over their neighbours. The hand keeps its position.

For example: 1 on C, then 3 on E: the hand stays, the fingers skip finger 2.

Fill

Keeps the position of the hand

Fill

Step by step through the space, one finger per key.

For example: 5-4-3-2-3-4: one finger per key, step by step.