Saturday, September 7, 2013

Cans of Word Worms: Now, Weight! Part Four

So here comes the "hardcore" physics part of the story.  Weight and mass are not the same thing. As defined in Part Three, mass is a constant, and weight changes depending on the force of gravity. This is why people become weightless in space, but they still have mass, because weight is determined by the force of gravity on mass. No gravity, no weight.

On Earth, the force of gravity (g) is a constant -
9.8 m/sec squared, to be precise. Simply put, a constant (g) times a constant (m) equals another constant. This is why the weight of an individual's arm doesn't change from note to note or measure to measure.

But SOMETHING has to change to change the sound, right? Here is where we go back to the one formula I asked you to learn: F=ma. Since we know that m is a constant for each individual's arm, we can reduce this formula one step further to F=a, or Force equals acceleration.

Larry Fine, expert piano technician and author of The Piano Book, now in its 4th edition and published by Alfred Music, has acknowledged that there are only three elements a pianist can change: the speed of the key descent, the speed of the key release, and the pedal. It is small wonder that Horowitz realized that playing the piano was all about timing. He didn't mean rhythm and duration alone. He also meant the subtleties of the timing of these three elements.

One more important point: acceleration and speed are also not the same thing. Acceleration is a CHANGE in speed over distance and time. If you look back at the piano action pictures in Part Three, you will see that the distances for movement in the action are also constant. We cannot change the distance between the hammer and the string, for example, in the middle of a performance.

We can, of course, change the distance the arm travels to reach the keys. This is why many teachers recommend playing close to the keys to control soft sounds. This is probably also why good ole Bugs Bunny was depicted playing Chopin's "Revolutionary Etude" with extreme arm movements. Each performer has a way of changing the acceleration of the key that may or may not include very large movements.

Okay, the hard part is over. The last installment will suggest ways to teach without the phrase "arm weight".

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