And though early pianos could produce both airy and thundering volumes, the instruments themselves couldn't always withstand the stylings of a fervent player—at least not until 1825 when the first iron-framed piano was patented. Pianos would crack apart under the hands of the instrument's early rockstars. "Before the iron frame, you had composers like Beethoven breaking pianos as they played them onstage," Isacoff said. "The instruments could not withstand the power of the players."

By the late 19th century, designers were still tinkering with piano design but—with generations of people trained on the piano as we know it—the window for adaptation was closing. The Hungarian musician Paul von Jankó introduced what came to be called the Jankó keyboard, which was shorter across but had several horizontal rows of keys like stripes across the instrument.

"It had 264 [keys] instead of the usual 88," Isacoff said. "They were arrayed not in the usual geometric pattern that we're used to seeing, so that you could play scales and difficult leaps and all kinds of challenging things that you find in keyboard music without moving your hand very much at all."

In 1911, an Australian designer insisted the piano of the future would have a curved keyboard with longer keys. "Instead of having to stretch and bend the wrist to reach the keys of the extremities of the keyboard, as the player must do with the straight keyboard" the Chicago-based Day Book reported that year, "he simply sweeps his arms in an arc of a circle."

Library of Congress

This alternative was, the newspaper declared, a "common sense keyboard," and yet it never took off. Neither did the Jankó for that matter. "The great Franz Liszt predicted that the Jankó would have replaced the regular keyboard in 50 years," Isacoff said. "All these predictions came to nothing. Once people are trained in a certain way, they don't want to have to relearn."

Which raises the question of what makes a piano a piano, anyway? Instruments, like many tools or technologies, are usually defined by function—that is, the meaning of the thing is often wrapped up in how we interact with it. So is a piano with a curved keyboard less of a piano than, say, a piano-mirror combo, or a piano built into a sewing table, or a piano combined with a fold-out bed—all of which are designs that were attempted at one point or another?

"This raises the question of whether an electric piano is really a piano or not," Isacoff said. "I'm on dangerous ground because, as a pianist who's in love with the acoustic instrument, I'm tempted to say 'no, it's not,' at which point people start throwing things at my head."

Is a piano still a piano if you play it with your feet?

"What is a piano? Well, think about why the piano evolved," Isacoff said. "The sound can swell into something huge and then diminish into a whisper. That adds a level of expressiveness to music making that is an essential component. Before the piano, you didn't have that. The piano was to get around this crippling deficiency."

The next question, then, is when does a piano stop being a piano? When does any technology slip away from the thing we call it and become, essentially, something else?

These days a phone can be a camera and a publishing system and a map and a diary and a recording device. And yet we still call it a phone. Even when it's a metronome. Even, yes, when it's a piano.

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