Sitting Position (1.1)

To find a balanced sitting position on the bench:

Lean backward from your hips, allowing your lower back to collapse and your head to fall forward.
Return gradually to an upright position by drawing your torso upward from the hips.
Bring your sit bones into the shape of the letter L, and maintain the gentle S-curve of the spine.
Your head should be balanced over your neck and spine.
Maintain an open torso.
Allow your shoulders to be comfortably dropped.
Your back is supported, but not arched as in a military posture.
Sit on the front half of the bench with your right foot next to the sustain pedal and the left foot flat on the floor, but at an angle that is a bit less than 90° at the knee.
Feel balanced on your bases of support in each foot and on the bench.
From this position, you should be able to rise to a standing position fairly easily just by leaning forward slightly from the hips and pushing upward from your left foot.

To adjust the bench height:

Bring both forearms up from your sides in a karate-chop position, with 5th fingers on the C's one octave away from middle C.
Rotate your forearms so that all fingers rest on the keys.
Adjust your bench to a height that allows your forearms to be parallel to the floor, or very slightly higher.
If your bench is too high and is not adjustable, find a lower one or a chair, and adjust height upward from there, if necessary.
Use flat, hard-cover books or carpet samples to add height in small increments.
For children and shorter adults who cannot easily reach the pedals, watch the next video.

Sit on the front portion of the bench.
Sit with your lower back supported—not slouched!
Try to sense your sit bones by collapsing backward and then returning to a more stabilised, upright position.

Place the bench so that your upper arm is slightly forward of perpendicular to the floor.
Your elbows should be slightly forward of your shoulders, to allow for mobility from side to side.

Sitting at a proper height for you, on the front portion of the bench, you're ready to gauge what distance from the keyboard feels optimal for you.
Try extending your arms outward, straight to the edge of the fallboard. For many pianists, this serves as a helpful gauge for distance, as when you drop your arms into a playing position, your elbows are likely to be slightly forward of your torso, allowing sufficient mobility.
Whether or not you use the "extended arms" test, check to see that when your hand comes to the keyboard that the angle created by your upper arm to your forearm is slightly forward of perpendicular, that is, at a slightly obtuse angle. If the angle is perpendicular, you are sitting too close, and your ability to move to different registers will be inhibited.

After setting yourself up at a proper height and distance, sitting on the front portion of the bench with good posture, consider your lateral alignment.
For most repertoire, aligning the center of your body opposite middle C or D tends to be optimal for accomplishing movement from register to register.

From your balanced sitting position in the last module, practise moving rotationally from the hips:

Turn your body to the left from your hips while keeping your rear in contact with the bench. (Note: Do not 'tip' to one side!)
Notice that your right knee moves forward as your body rotates to the left.
Turn your body back to centre and then to the right, again maintaining full contact with the bench.
As your body rotates to the right, your left knee moves forward, and slightly to the right.
Experiment with moving back and forth in a 'skiing motion,' allowing your torso and spine to move rotationally.
Practise moving both hands and arms to the left and right sides of the keyboard, at the same time, about 1-2 octaves apart.
Mobility in the hips results in smooth movement from register to register, even when both hands move together to the extremes.
Notice your knees moving forward and backward, but continue to imagine the movement coming from the hips.

Review posture, sitting position, rotational mobility of the hips, and bench height and distance.

Sitting well is job number one!

Sitting well sets the stage for optimal coordination in all movements.