Violinist Anne-Sophie Mutter and pianist Lambert Orkis perform at Strathmore on Tuesday. (Susan Biddle/FOR THE WASHINGTON POST)

When Lambert Orkis does something, he does it thoroughly. He’s interested in birds, so he gets expensive cameras and lenses and learns how to photograph them like a professional. He’s interested in early pianos, so he owns five of them. He’s interested in collaborative piano, so he has been working with the violinist Anne-Sophie Mutter for 25 years — since shortly before her Carnegie Hall debut in 1988. They’ll celebrate that anniversary with a joint appearance in December, and they’re leading up to it with several bouts of touring, one of which will bring them to Strathmore on Tuesday night.

Mutter is one of the world’s leading violinists. Orkis is a little harder to pin down. Few pianists are “just” accompanists, but Orkis’s breadth of interests have added up to an uncommonly rich musical life. Go to a National Symphony Orchestra concert and you may see him sitting in the back of the orchestra as its principal keyboardist; he’s also sat in front of it playing a concerto at Carnegie Hall. You can hear him with the Kennedy Center Chamber Players, which he co-founded in 2003, or playing on historical instruments with the Smithsonian Castle Trio at the National Museum of American History. A number of living composers have written new works for him — George Crumb, Richard Wernick, James Primrosch. Yet one of his main focuses is the very old: playing and recording Beethoven, for example, on the kind of instruments Beethoven would actually have used.

“The only map I had for my performing life,” said Orkis, now 66, from his home in Virginia last week, “was I enjoyed playing the piano.”

Collaborative piano gets a bad rap. Once you are labeled “accompanist,” you risk being overshadowed by a more famous partner. You have to do a lot of the heavy lifting onstage; you often take part in repertory planning (Orkis suggests works to Mutter, and vice versa); but you don’t always get an equal share of the glory. “It is funny,” says the pianist Inon Barnatan, a soloist who also works with the cellist Alisa Weilerstein, “how a cello and piano recital can quickly become a cello recital, in terms of how people view it.”

Orkis knows a thing or two about that. Before Mutter, his regular instrumental partner was the great cellist Mstislav Rostropovich, who as the NSO’s music director also brought Orkis to the orchestra. While the two men became close personal friends over 11 years, their work wasn’t exactly a partnership of equals. “He personally knew the composers of a number of the pieces that we played,” Orkis says, citing Shostakovich, Prokofiev and Britten. “He’d been playing these pieces for many years. I wasn’t about to say a lot of things to him.” Playing with Rostropovich, he says, was like “riding a tiger.”

Cellist Mstislav Rostropovich and pianist Lambert Orkis in concert. (From Lambert Orkis)

With Mutter, however, there has been more give-and-take — not least because Orkis has been working with her since early in her career. In fact, the two first met when Mutter came to Washington at 16 to make her NSO debut under Rostropovich in 1980. She performed Mozart’s third concerto; but to Mutter’s recollection, it was the Glazunov concerto she ran through in private for the maestro, with a rehearsal pianist she didn’t know. “He already stood out,” she recalled last week, speaking by phone from her hotel room in San Francisco a few hours before she was scheduled to take the stage with that erstwhile rehearsal pianist. “This was a musician who works with you, brings his own ideas.” At the time, though, she was playing with the pianist Alexis Weissenberg, and it took several years for her and Orkis — again at Rostropovich’s instigation — to start working together.

A musical partnership is intangible. But you know it when you feel it. Mutter cites something conductor Kurt Masur said about collaborative playing: “You have to sense the soloist. If you wait until you see and hear him, it’s already too late.” In other words, you have to be together even before the music starts — which, she says, is what happened with her and Orkis: “We both noticed we had the same breath and phrasing, and feeling for what the other one was doing.”

They’re also both workhorses. Both of them have played thousands of times. Orkis has been playing collaboratively since he was getting his doctorate at Temple University and got a job accompanying student recitals; “the first year,” he says, “I played for 47 people.” (He still teaches at Temple, a job he’s held since 1968.) Many musicians at this level might feel that certain pieces were secure. Yet they rehearse at great length, even pieces they know intimately, like the Schubert C Major Fantasie, which they’ll play on Tuesday. “It’s an unusually personal and deep work,” Mutter says, “so we always start from the beginning.” And even on tour, when many top musicians get into a groove, Orkis and Mutter rehearse for an hour or so before each performance, trying out the piano, running through the pieces, and going out into the hall to listen to each other and figure out where the best place is to stand onstage.

“Think of athletes,” Mutter says. “Roger Federer has played countless times at Roland Garros, [the site of the French Open], but the ball may bounce a certain way on a certain day. You can never take anything for granted. There is no routine.”

“We have better performances” as a result of all the rehearsing, Orkis says. “I think the audience feels the difference.”

Orkis comes from a family of hard workers — of working-class first-generation European immigrants. “My father was bringing home $100 a week,” he says, “and at one point was putting away $25 of that for a piano lesson.” The piano in the home was a sign of status; Orkis’s Polish-born grandmother (the original name was Orkwiszewski) worked as a housekeeper in Philadelphia after her husband died but managed to save up enough for an upright, and Orkis’s father followed suit. Still, no one foresaw that Orkis, who wanted to take lessons like his big brother, would end up at the prestigious Curtis Institute. “He has talent for music, my brother,” Orkis says, “but he’s not one to slug it out. I have some talent for music, but I have a lot of patience.”

That tenacity is a boon to his musical life. “It’s this kind of obsession with various things or stylistic issues that characterizes his deep involvement,” says Kenneth Slowik, artistic director of the Smithsonian Chamber Music Society, and a fellow member of the Castle Trio — citing not only musical issues, but also Orkis’s expertise in birds, tea or the Russian Blue cats that are the pride and joy of him and his wife, Jan.

And it’s led Orkis through a couple of epiphanies that have helped shape his career. Take his first encounter with Messiaen’s “Quartet for the End of Time,” when he was called to substitute for a sick pianist in a performance; when he looked at the score, he says, “it was as though skies had been torn asunder.” It was the start of an intense relationship with contemporary music. At a certain point, though, Orkis, tired of learning more and more new pieces that were never going to be performed again — an occupational hazard of contemporary music since Mozart’s day — “felt something was missing from my life.” It was then that Slowik introduced him to the Smithsonian’s collection of historical instruments, starting a passion that has allowed Orkis to record some repertory staples — the complete Beethoven concertos, for instance — in addition to his award-winning activities with other musicians (he and Mutter won a Grammy in 2000 for a disc of Beethoven sonatas).

These days, a so-called accompanist may not be automatically doomed to play second fiddle. “I do think that times are changing a little bit,” says Barnatan, “and people are able to appreciate musicians doing a lot of different things, rather than the traditional boxes of either soloist or just doing recitals or just doing contemporary.” Barnatan’s collaboration with Weilerstein has in some cases helped further his solo career; the Washington Performing Arts Society, for example, reengaged for his own solo recital this past October.

And what ultimately sustains, of course, is simple love of the music — and an occasional moment, after all, of resting on your laurels, audible when Orkis brings up the Saint-Saens sonata he and Mutter will play at Strathmore.

“We’ve made it our own,” he says. “We figured out how to make this thing work. It’s not the most incredible sonata in the world. But it’s so much fun to play.”

Anne-Sophie Mutterand Lambert Orkis

in a Washington Performing Arts Society presentation at Strathmore on Tuesday at 8 p.m.