Bell tones from the piano

Murray Campbell’s article “Evaluating musical instruments” (Physics Today, April 2014, page 35 ) was quite interesting. A statement in the section “What makes an excellent piano?” particularly caught my eye. Campbell writes, “Some pianists believe that by merely altering the manner in which the key is depressed, it is possible to change the timbre of a single note, without altering its loudness. It is hard to see how that can be true.”

In one of Camille Saint-Saëns’s piano concertos—I forget which one—a key is struck in such a way that it produces a bell-like tone. I asked a virtuoso pianist about it after hearing him play the concerto (this was 30 years ago), and he said that what we heard was a harmonic. He had to strike a key in a certain way to achieve it, and each piano was different in regard to the technique required. He said that to get it right for the concert, he had to experiment with that particular Steinway. I’d love to learn more about the technique involved.