NEW YORK (NYT NEWS SERVICE).- The music of Thomas Adès isn’t easy — not for listeners, and especially not for performers. His style, whether in a small solo or a work on the grand scale of his opera “The Exterminating Angel,” is full of contradictions: looking more complex than it sounds, teasing the ear with elusively familiar melodic strands, evoking clutter with meticulous precision.

Even for pianist Kirill Gerstein, one of Adès’ most capable interpreters, it exists precariously at the edge of possibility. “If you practice a lot,” Gerstein said in a recent interview, “it’s almost comfortable.”

That might be a tad too humble coming from Gerstein, who over the past decade has become a master of Adès’ piano works — and a muse. In one of the most productive and thrilling artistic partnerships of our time, they have not only toured together and revisited older pieces in virtuosic arrangements but also produced a piano concerto that has been that rarity in contemporary classical music: a hit.

Now their friendship is bearing fruit for a broader audience. That piano concerto, which premiered with the Boston Symphony Orchestra last year, was recorded by Deutsche Grammophon and released in February. And Gerstein’s latest album, out from the Myrios label May 15, will feature the composer and pianist in the first recordings of “Concert Paraphrase on ‘Powder Her Face,’” for two pianos, and a solo arrangement from “The Exterminating Angel” as well as three mazurkas and the concertolike “In Seven Days.”

The two albums offer a bird’s-eye view of what, in retrospect, feels simply like “a natural evolution,” Adès said from his home in London in a recent video call with Gerstein, who was in Berlin. Even the concerto, they noted, came about not as a commissioned mandate but from a casual conversation.

In 2012, Adès was in New York rehearsing “The Tempest” with the Metropolitan Opera while also preparing a performance of “In Seven Days,” a work originally written for Nicolas Hodges, with Gerstein and the Boston Symphony. (The Myrios recording of the piece was made in 2018 at Tanglewood, that orchestra’s summer home.) During a break, Gerstein asked Adès whether he’d consider writing something for him.

“Does it have to be a solo piece?” Adès responded. He was interested, he said, in writing “a proper piano concerto” — with a more traditional form than the idiosyncratic “In Seven Days.” And he had a feeling that if he wrote one, Gerstein would be able to pull it off.

“I knew I wouldn’t be faced with a situation of explaining to someone what my language is,” Adès recalled. “Very often someone can play perfectly from the text, but somehow still the music gets lost somewhere. I knew that wasn’t going to happen.”

Although Adès has been confronted with artists who find his works, as he said, “totally weird,” Gerstein described it, with deceptive simplicity, as “music just like any music.” That doesn’t mean it didn’t require getting used to, particularly the way Adès shapes time.

“The musical flow and rubato leave room for interpretation, but he precisely controls it,” Gerstein said. “This sense of time that’s not square is a general trend of great composers, but I think Tom has specific means to make the performer do what the music needs.”

Time, in Adès’ scores, is noted in specific detail that can be daunting at first glance. The second mazurka even comes with two versions of the right-hand line: one labeled “play this,” and a simpler one above, “hear this.” In “Concert Paraphrase on ‘Powder Her Face,’” one standard, four-beat measure is distorted by tuplets of varying lengths.

“For me,” Adès said, “the creative reality is on the edge of chaos.”

Gerstein relishes difficulties like these. “That’s what virtuosity is,” he said. “It’s not a given.”

Adès interjected: “If it were a given, it wouldn’t be fun.”

That’s especially the case in the “Powder Her Face” paraphrase, arranged for two pianos in 2015, which Gerstein and Adès toured together before recording on the new album. The piece’s cohesion — amid disarray and rollicking irony — doesn’t ever seem like a guarantee. Indeed, Gerstein recalled a rehearsal in which Adès said something like, “This is very interesting for me, what you misread.”

But they communicated fixes easily, with metaphors. Another piece recorded for the first time on the new album is a solo version of the Berceuse from “The Exterminating Angel” — a late scene, of alluring yet slippery harmonies, in which two lovers steal away to a cabinet to kill themselves. It had a tempo change that Gerstein didn’t quite understand.

A calando — a direction to gradually diminish — is stretched over several measures, then the words “molto più” are written above a final measure before a section labeled “tempo giusto,” with a metronome marking of “circa 46.” Gerstein wanted to know how the transition should sound, and Adès told him, “It’s like a choir in a church, and they know what they’re singing so well, they’re singing with their eyes closed. And when that happens, they’re ever so slightly quicker.”

“You can have the ‘tempo giusto’ and the metronome marking,” Gerstein said, “but I hear that and I know exactly what wind in the ‘tempo giusto’ you need.”

Over time, Gerstein has also internalized some of the ways Adès’ work interacts with and builds on the past, evasively referential but never derivative — particularly in the Frédéric Chopinesque mazurkas. “Tom’s writing has these DNA fragments of the great examples of the piano literature,” he said, “and at the same time they’re reconfigured and sometimes genetically engineered to do other things.”

This is true of the Concerto for Piano and Orchestra, which Adès conducted in its premiere with the Boston Symphony. It has the banal title and formal appearance of a piece that could have been written two centuries ago. Yet, as in much of this composer’s work, familiarity repeatedly gives way to novelty — above all in its harmonic language and rhythmic flow.

Although the concerto was written with Gerstein’s facility — a dazzling dexterity that thrives in both Sergei Rachmaninoff and jazz — in mind, Adès didn’t give him the score until it was finished. While reading through it, Gerstein sent videos that came as a comfort to the composer.

“I found it very moving to think of how lonely a road it must be,” Gerstein said. “When you’re writing, you are really with this thing alone. But when an interpreter joins the piece, this road is no longer traveled by one person.”

The videos were also a venue for suggestions of edits — a digital analogue to Johannes Brahms finishing his Violin Concerto with the help of the soloist, his friend Joseph Joachim.

“He understood the piano writing so well,” Adès recalled. “He said, ‘Should we try this?’ and I think with all of them, I ended up saying yes, after resisting in all the usual ways.”

But there was no budging on the concerto’s difficulty, which not even Adès — a skilled pianist who has performed his own works, including “In Seven Days” — could manage from start to finish. One knotty passage, in which a canon slides out of sync, continued to give Gerstein trouble until, once again, an image from Adès helped, though this one was more motivational then metaphorical: Disney’s Hercules as a baby twisting snakes into submission.

The concerto has already become a well-traveled success. Shortly after the premiere, it received a standing ovation at Carnegie Hall, and within a year it had been booked for 50 performances and counting — a popularity practically unheard-of in classical music. In an even more unusual move, the Boston Symphony recently announced that the concerto would return next February, again with Adès and Gerstein.

They were scheduled to give the Los Angeles premiere at Walt Disney Concert Hall in April, but the concert was canceled because of the coronavirus pandemic. It would have been an opportunity not only to bring the piece to one of the cities Adès calls home but also for the two friends to reunite.

When they’re together, they talk about music, naturally, but for only a short time. “To me it’s a very dear friendship,” Gerstein said, “a multithreaded friendship.”

Often, they share a good meal. “That’s Kirill,” Adès said. “He always knows where to go.”

They are also supportive of each other’s work. Gerstein made a trip to the Salzburg Festival in 2016 to see the premiere of “The Exterminating Angel.” It was then that he fell for the Berceuse; over dinner, Gerstein said that he loved that scene, and Adès replied, “I can arrange that as a piano piece.”

It is brief — about 5 1/2 minutes long — but it’s the highlight of Gerstein’s new album, a dangerous lure of captivating harmonies that give way to a horrifying rumble. Adès described the ending to Gerstein as “staring down the jaws of a serpent.”

They have been revisiting the piece recently while putting the finishing touches on the Myrios album — something they’ve had a luxurious amount of time for during quarantine. Adès, as his scores make clear, can be exacting about details. But when he listens to Gerstein play his music, he feels like he never has to worry.

“I can relax, which is unusual for me,” Adès said. “It’s one of the only moments I can relax.”

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