The conductor Valery Gergiev is alternately maddening and brilliant, sometimes both - as he and his Mariinsky Orchestra showed Sunday night at the Kennedy Center. (Alexander Shapunov )

“Reliably erratic” may sound like an oxymoron, but the term perfectly describes the conductor Valery Gergiev. His name is almost synonymous with the Mariinsky Orchestra and Theater, which he has led since 1988, and which he has turned into a veritable musical factory, touring and recording and performing at a pace unknown to most mortals. When he conducts, which is nearly every night, be it in St. Petersburg or New York or, on Sunday night, at the Kennedy Center, he plunges into the music with a kind of mania that seems at the edge of exhaustion (there are stories about him nodding off while leading an opera). He is authoritarian and old-school and fiercely defends his music and his players, with whom he stands on the same level, on the floor, eschewing the traditional podium, conducting with a toothpick. (This is not a poetic euphemism. He literally conducts with a toothpick on occasion, and on Sunday.) Sometimes the result is kind of brilliant, and sometimes it’s a big mess, but either way, there’s usually a sense of excitement that makes audiences want to come back for more.

Sunday’s performance, presented by Washington Performing Arts, was tilted toward the “mess” end of the spectrum. Gergiev’s next stop with the orchestra is Carnegie Hall on Tuesday and Wednesday, and the players conveyed the sense of being at a dress rehearsal, tired and unconcerned about details like intonation. Strauss’s “Don Juan,” a colorful tone poem, came off less as a clear picture than as a pile of broken crayons — albeit passionately broken. Even on an off night, Gergiev makes it hard not to listen.

The evening contained some curiosities. It opened with Alexander Mosolov’s “Iron Foundry,” a 1920s-vintage depiction of the sounds of a factory, bristling with brass and percussion and redolent of the oily energy of that period’s brave new world.

Even more curious was the main event: the (first) piano concerto by the brilliant pianist Daniil Trifonov. Gergiev has been championing Trifonov since he chaired the jury of the Tchaikovsky competition when the young pianist won it in 2011 (he first brought him to the D.C. area later that year). Today, Trifonov is launched on a top-tier career. He is also honing his voice as a composer, on the model of Rachmaninoff, who wrote his challenging piano music as a vehicle for himself.

I use the term “on the model of” advisedly, because Trifonov’s long concerto sounded a lot as if Rachmaninoff had written it. Conceived on a grand scale, packed with Romantic melody and virtuosic fingerwork, it offered a lot of surface color and activity, and generally behaved the way that lovers of the classical canon believe a piano concerto should: a well-bred child of the early 20th century, eager to show its stuff. It reminded me of a children’s book my son has about a child ghost named Leo — a small figure in period costume, moving engagingly through the modern world, with no corporeal substance whatsoever. Trifonov, of course, played brilliantly and with deep involvement, and, as an encore, showed another gifted pianist poking at melody: Alfred Cortot’s arrangement of the third movement of Chopin’s cello sonata.

But then, after the intermission, the orchestra had a lot more to offer in Prokofiev’s Sixth Symphony. It’s a wonderful piece, for one thing, with its juxtapositions of force and lyricism, and the orchestra, though it didn’t give an elegant performance, made a forceful case for it. Perhaps the musicians were warming up. More important, given their relentless schedule — they were slated to play a private concert in Washington on Monday night — they might make good use of more time to cool down.