Touching a chord

Touching a chord

A University of Waterloo engineer seeks to discover how touch can change a piano’s sound
October 24, 2008
Whether it’s Billy Joel pounding out Piano Man or the kid next door muddling through Chopsticks, few pianists understand the complex mechanics that occur between their fingertips and the sound emerging from their instrument.

Teasing out the complex series of mechanical joints, levers, and acoustic engineering of the piano is the job of Stephen Birkett, an associate professor of Systems Engineering and leader of the Piano Design Laboratory at the University of Waterloo in southern Ontario.

Birkett, who is also an Associate of the Royal Conservatory of Music—one of the highest honours a performance pianist can receive—has spent several years modeling how a piano hammer strikes the strings to emit various sounds. In doing so, he may have found the answer to an age-old musical question: does a pianist’s touch influence the tone of a note?

Many music lovers will tell you that the way a pianist presses the keys affects whether the sound is “tinny and percussive” or “round and mellow.” If, for example, you took two pianists with different playing styles and had them play the same note at the same loudness, each note would seem to have a slightly different quality of sound. This could be a function of touch.

When you learn how to play, you learn different methods for touch,” says Birkett. “But physicists will argue that you can’t influence anything but the hammer velocity.” Birkett’s research, however, has revealed that vibrations could cause the hammer to act differently when it hits the string.

It is impossible to accurately measure the minute movement of the hammers with a real piano and pianist because the space inside a piano is too restrictive and a pianist’s touch is too inconsistent. Plus, a piano’s parts are so small that attaching sensors would cause radical changes in movement. So Birkett designed single key models of various piano types from different time periods and used a mechanical finger to press the keys at a constant and consistent pressure. With each press, several high-speed cameras recorded the motion of crucial joints and pieces.

By analyzing these motions, Birkett has potentially found the root cause of the debate.

Over the centuries, piano designs have become louder and more responsive to fast movements as key action evolved from a simple lever to a complicated series of precisely crafted levers and joints.  In fact, the post holding the hammer in a modern-day piano looks unshakeable compared to its almost flimsy ancestor. Birkett discovered that hammers in 200-year-old pianos vibrated significantly,  suggesting that instruments from that era do allow musicians to have a greater influence on the tone of a note. He has yet to determine how much hammer vibrations vary in modern pianos but plans to make that the focus of his upcoming research.

Ultimately, Birkett hopes his research into a piano’s inner workings will help pianists determine what is musically and scientifically possible through various playing styles.

"For a lot of pianists, all you do is play keys. But to really understand your instrument and what you can do with it, you have to look behind the keywell,” says Birkett. You need to see the whole picture.