BERLIN.- Phyllis Chen began studying the piano at age 5, learning from a strict, traditional teacher who taught her the standard repertoire. She was a passionate musician, but sometimes wondered how much of her playing was artistic, rather than purely athletic.

“I never found it to be entirely fulfilling,” Chen said in a video interview. “I always thought there was something missing.”

Chen, 45, was pursuing graduate studies at Indiana University when she first encountered the toy piano, an instrument with a brittle, xylophone-like sound usually around 20 inches long, with a range of three octaves. Her teacher, virtuoso pianist André Watts, was a Franz Liszt specialist but encouraged her to pursue her own interests.

Once, Watts tried Chen’s toy piano; the keys were so small and his hands so big that he struggled to play a single note at a time. But for her, playing the unusual instrument was liberating. “I was very excited to be able to explore without all of the traditional boundaries being tied to it,” she said. “No one was going to tell me: ‘This is the canon of works. This is how it needs to be played.’”

She is among the growing number of keyboardists expanding their practice beyond the modern piano — that instrument so central to classical music, with its large and historically important repertoire, orchestral heft and essential role in teaching. But for these pianists, learning to play other keyboards has been invigorating. On these less prominent instruments, they have explored unfamiliar timbral terrain, reexamined their approaches to canonical works and created new repertoire. They return to the modern piano with greater aural and tactile sensitivity, feeling a renewed sense of freedom and purpose at the instrument.

Chen was a founding member of the International Contemporary Ensemble in 2001. A few years later, she was extremely busy, traveling between New York and Chicago to perform and attending university in Bloomington, Indiana, when she got tendinitis in both arms.

She found the toy piano less painful to play than the grand piano, and began to focus on it. “People would say: ‘Well, don’t you find that very limiting? The range is smaller,’” she recalled. “I thought the sound itself was an unexplored sound.”

With the toy piano, Chen was entering a less crowded field. “The piano being something that is so fully explored — even with its large range — it felt like there were a lot of limits on what I could do,” she said.

Because of the modern piano’s role in classical music training, keyboardists must often go to significant lengths to familiarize themselves with other instruments. When Alexei Lubimov was a student at the Moscow Conservatory, he became interested in historical keyboards. There were few such instruments available in the Soviet Union in the late 1970s, so Lubimov, now 79, persuaded the Moscow State Academic Philharmonic to buy one: a fortepiano by German historical instrument builder J.C. Neupert, in the style of Wolfgang Amadeus Mozart’s time. Lubimov believed it to be the only playable fortepiano from that era in the city. “All the other instruments that I knew in Moscow,” he said in a phone interview, “were in museums.”

Lubimov’s encounter with the Neupert fortepiano proved decisive. For three years, he hardly practiced the modern piano. He reworked his technique from the ground up, lightening his touch and giving his ear time to adjust to the fortepiano’s sound quality, with its subtler dynamic shadings. He studied historical treatises on aesthetics, phrasing and articulation, wanting to understand how the instrument was played. “The adjustment was a really difficult task for me at the time,” he said, “because I had to push aside my musical environment and a whole world of habits.”

When he returned to the modern piano, it was with the epiphany that “every instrument is a part of the chain of development,” he said. Some music, like Galina Ustvolskaya’s transcendentally brutal piano sonatas, requires the full force of a concert grand; other pieces, like Ludwig van Beethoven’s piano works, were clearly composed around the idiosyncratic capabilities of historical instruments.

“I don’t want to modify Beethoven for the modern piano as many pianists do or try to attempt his instructions on a modern instrument,” Lubimov said. “Beethoven’s ideas come alive all by themselves on practically every historical instrument.”

In 2011, Lubimov recorded Beethoven’s last three piano sonatas on an Alois Graff fortepiano from 1828. Individual voices emerge clearly from dense contrapuntal passages; melodies that would sing easily on a modern piano gain a plaintive fragility because of the older instrument’s shorter sustain. Lubimov has decided never to play Beethoven’s solo pieces on a modern piano again.

Like Lubimov, Jacob Greenberg first dived into other keyboard instruments while at conservatory. He now plays modern piano, electric piano, celesta, harpsichord, harmonium, shrutibox, toy piano and pipe organ.

In September, Greenberg traveled from his home in Berlin to Rostock, Germany, to build his own clavichord: a small rectangular keyboard instrument that was most popular from the late Middle Ages to the early classical period. The clavichord’s sound is so soft, it is mainly used for private practice or as a composition aid.

For eight days, 11 hours a day, Greenberg, 49, worked on his clavichord in a wood shop belonging to instrument builder Johann-Gottfried Schmidt. All the work with band saws, power sanders, drills, clamps, hammers and other tools was nerve-wracking for Greenberg. “The risk of messing up the instrument was at least as great as the risk of injuring yourself,” he said.

Still, building the clavichord was enlightening. Greenberg took particular pleasure in tuning the instrument, and in the delicate process of evening out the weight of the keys so that they would feel consistent across the clavichord’s range. The workshop “gave me so many interesting insights into the instrument,” he said. The finished product has a complex, bittersweet sound, and fits neatly inside a wooden box.

Creating the instrument was a culmination of Greenberg’s decision to work with a wider range of keyboards. His 2021 album “Bright Codes,” made up entirely of new commissions, includes pieces for modern piano, but also for harmonium (a kind of reed organ) by Ione, Dai Fujikura and Nathan Davis. In their pieces for harmonium, long, nasal chords float slowly past — a timbre the piano doesn’t have, at a pace it couldn’t sustain.

“Past a certain point,” Greenberg said, “I needed the experience on nonpiano keyboards to keep being inspired for my piano work.”

Like Greenberg, some keyboardists now incorporate multiple instruments into a single recital or album. Last year, Alexander Melnikov, who often performs on instruments from different epochs, released the album “Fantasie: Seven Composers, Seven Keyboards,” with pieces by composers from Johann Sebastian Bach in the 18th century to Alfred Schnittke in the 20th, and instruments including harpsichord and modern piano.

With practice, keyboardists learn to adjust quickly from one instrument to the next, as an orchestral clarinetist might play three kinds of clarinets in a single symphony. All keyboards have differences, and adapting to an unfamiliar instrument is an important skill for pianists. But those differences are more pronounced among historical instruments. “Within a given category,” Melnikov, 51, said in an email, “the differences between different makers and individual instruments of the same makers with be much bigger than the differences between modern pianos.”

For some keyboardists, that is part of the appeal. “It was clear that every instrument is unique,” Lubimov said of historical pianos. “This unbelievable variety and difference makes this journey and history so interesting, so delightful, so magnificent. And that does something to the player.”

When keyboardists return to the modern piano, their ideas of what it can do are expanded. “Very often, I hear that on modern I sound ‘different’ or ‘more historic,’ even that I am absolutely unaware of doing anything like this,” Melnikov said.

The experience changes the way artists hear themselves, too. “You’re aware of every aspect of the envelope, and you can just listen for so much more,” Greenberg said. “You’re curious about so much more.”

That was true for Chen, who in 2007 began UnCaged Toy Piano, a composition competition and festival whose goal was to develop the repertoire for the instrument. In organizing the performances, Chen often shared ideas for toy piano pieces with composers, one of whom told her, “If you have all these ideas, then I think you should be writing for it.”

Chen was a trained pianist, not a composer; she worried she’d be considered a dilettante, so she wrote her first pieces under pseudonyms. Then a friend wanted to play a toy piano work by Elsa Brunswick and asked Chen for Brunswick’s contact information. Brunswick, of course, was Chen.

It was the playful quality of the toy piano that gave her the confidence to pursue her own compositions. The grand piano “always felt very serious,” she said. Writing for the smaller instrument was “a childlike feeling of finding the loophole.”

Recently, Chen has returned to the modern piano on her own terms. Piano keys are black and white; now, Chen is working with shades between. Her 2019 composition for piano “SumiTones” uses five shades of gray notes to show how foregrounded or backgrounded tones should be. (The work is dedicated to Greenberg.)

“Toy piano has helped open up some doors and made me feel less pressure,” Chen said. “And I feel like I can actually bring that back to the piano as well.”

This article originally appeared in The New York Times.