10 years ago by
A Pianist
If you are tightening the stomach, you are constricting yourself. The back comprises the spine and the ribs - they should know how to be vertical on their own, without the help of the stomach. Tightening the stomach is a misguided attempt to help the back rise up into verticality. But the back has extensor muscles which are designed to do this. When they aren't working properly, many people use the stomach to help. This is a mistake.
The knees should be either level with the hips or very slightly lower, never above. I myself have a problem with this because I am very tall but must sit low at the piano. I have found a way to sit well with my knees higher than my hip joints, but it is tricky to find it.
AFF