This weekend’s program from Andris Nelsons and the Boston Symphony Orchestra at Symphony Hall couples two 20^th-century Russian masterpieces. Each work runs 40-45 minutes; each takes liberties with form. One, Rachmaninov’s Piano Concerto No. 3, is blisteringly familiar, even notorious; it’s the hyperromantic ultimate of concertos, and the most demanding in terms of technique. The other, Shostakovich’s Symphony No. 15, is unfamiliar even by Shostakovich standards, and it’s notorious only in that no one is quite sure what, in his final symphony, Dmitri was trying to say. On Thursday, Russian guest soloist Daniil Trifonov gave an individual and not altogether gratifying reading of the concerto, but Nelsons continued his fine run of Shostakovich interpretations.

The Rachmaninov even has, unusually for a piano concerto, its own nickname, variously “Rach 3” or “Rock 3.” Rachmaninov wrote the piece for his 1909 American tour, dedicating it to his friend Josef Hofmann, but for a time it seemed the composer himself, with his huge hands and long fingers, was the only pianist capable of performing it. The close-knit theme that opens the “Allegro ma non tanto” is child’s play (i.e., you or I could manage it); it’s been likened to a folk tune, or Russian Orthodox chant, though Rachmaninov insisted that “It simply wrote itself!” When I listen to the opening notes of Byron Janis’s 1961 recording, I hear the wind whipping down St. Petersburg’s Nevsky Prospect, but you might equally hear church bells or a folk dance — the tune is innocent and ambiguous enough to encompass all Russia. The second theme is more contemporary, blue even before the composer heard Gershwin, and it keeps its shape, wistful and reflective, while the first theme explodes into pianistic fireworks, from the initial statement (where the soloist has a mini-cadenza) on into the development and then the true cadenza, for which Rachmaninov provided two alternatives.

The “Intermezzo: Adagio” brings another seemingly simple tune that, in the course of its variations, erupts into remorse and regret before that opening theme from the “Allegro ma non tanto” makes a surprise guest appearance. The “Alla Breve” finale looks conventional enough, with a driving first theme that presages the blizzard in Aleksandr Blok’s “The Twelve” and then an upward-striving second, but where you expect development, you get another surprise, the “blue” theme from the first movement, underappreciated there, coming into its own here, like Cinderella. The upward-striving theme that controls the concerto’s climax, but it’s the “blue” theme that lingers.

Rachmaninov himself recorded the concerto in 1939–40, with Eugene Ormandy and the Philadelphia Orchestra, but it was Vladimir Horowitz who made it famous. Horowitz’s tense, driven readings — which, like Rachmaninov’s, observed the composer’s suggested cuts — ruled the record roost until 1959, when RCA (Horowitz’s label, and also Rachmaninov’s) released Van Cliburn’s Carnegie Hall appearance with Kirill Kondrashin and the Symphony of the Air. Cliburn set a new standard for the Third: uncut, expansive, heroic, and lush. Further recorded landmarks have included Martha Argerich’s volcanic 1982 reading and, inevitably, the one-of-a-kind 1995 account from David Helfgott, whose life story inspired the 1996 film Shine. There’s no one way to play the piece; my own favorites include Janis (more like Horowitz), Evgeny Mogilevsky (more like Cliburn), and Alexis Weissenberg (not like anyone else).

Just 28, Trifonov is already a high-profile artist; he took first prize at the 2011 International Tchaikovsky Competition, and like the orchestra he’s a recent Grammy winner, for his complete Liszt Études. I had been impressed by his 2012 recording (with Valery Gergiev and the Orchestra of the Mariinsky Theatre) of the Tchaikovsky First, where he scraped away the bombast, and by his interpretation of Mozart’s No. 21 (the one whose Andante Elvira Madigan immortalized) with Nelsons and the BSO two seasons ago at Tanglewood, which was so patient and limpid, I found myself recalling Dinu Lipatti.

Nothing could have sounded less like Lipatti than what Trifonov offered Thursday. If I’d been blindfolded, I’d have tconcluded I was listening to Lang Lang on a particularly personalized night. Nelsons got the piece off to a quick start, which was fine, but Trifonov was oddly offhand in that first theme, which neither chanted nor danced. The solo French horn that takes up the theme after some 30 bars is marked piano, same as the piano (which has accompanying passagework), but here it swamped Trifonov. And then his mini-cadenza was a clattering torrent in which melody and even rhythm got submerged.

The second theme was as offhand as the first, and it was followed by a nervous, hectic development in which everything ran together and Trifonov seemed to want to prove he could play faster than Argerich. The thunderous, overwrought cadenza, on the other hand, all but stopped time; I’d have called it heaven-storming except in this case heaven wouldn’t be high enough. (This was the heavier, darker, “ossia” version rather than the more toccata-like one that Rachmaninov himself favored.) The second theme, when it returned, was a taffy pull.

The Adagio brought a torrential entrance from the piano — nothing wrong with that, but the theme rambled and in the first variation I heard only left hand. The big climax seemed angry rather than impassioned, and here again the wind and French horn solos, at least from where I was sitting on the floor, sounded overbalanced. Trifonov accelerated dramatically into the finale, where the first theme disintegrated into a cascade of notes with hammering bass, the second had a metallic clang, and the return of the second theme from the first movement brought more self-conscious “poetry.” Even the orchestra began to sound crass, and its decibel level at the climax was more than Trifonov could handle.

This concerto — for better and worse, mostly better — has become not only a technical showpiece but an interpretive one, and in live performance it’s an opportunity to explore ideas. Trifonov’s reading Thursday was quite different from the one he gave with Myung-Whun Chung and the Orchestre Philharmonique de Radio France in 2015, and possibly quite different from the 2017 reading he did with Gustavo Dudamel and the Los Angeles Philharmonic, where Alex Ross found in the first-movement cadenza “a tragic heft that changed the meaning of the concerto around it.” What I heard only seemed to distort the meaning of the concerto around it. Rachmaninov’s own recording is notably chaste, but a pianist doesn’t have to take the piece apart to put a personal stamp on it the way, say, Anna Fedorova does.

Even the one encore, the Andante sognando second movement from Prokofiev’s Piano Sonata No. 8, just rolled along. It’s only fair to add that Trifonov exudes integrity at the piano and humility away from it, as in the respectful way he shook hands with both first associate concertmaster Tamara Smirnova and associate concertmaster Alexander Velinzon before seating himself.

If Trifonov perhaps failed Rachmaninov by trying to do too much, Nelsons succeeded in the Shostakovich by seeming to do nothing at all. Thursday’s presentation of the Fifteenth was by no means the BSO’s first. After Eugene Ormandy had led the American premiere with the Philadelphia Orchestra in 1972, Maxim Shostakovich — the composer’s son — gave the BSO premiere in 1981, and there have been subsequent performances by Kurt Sanderling in 1988, assistant BSO conductor Richard Westerfield in 1997, and assistant BSO conductor Andris Poga just five years ago, in 2014. But Nelsons is the first BSO music director to conduct the work, and this reading will eventually appear, on Deutsche Grammophon, as part of his complete Shostakovich cycle, which so far has garnered three Grammy awards in as many tries and given the orchestra a composer it can call its own. Nelsons’s particular approach steers a relaxed but alert interpretative course between the political and the prosaic where, instead of trying to provide the right answers, he asks the right questions. 

Shostakovich composed the Fifteenth in 1971, four years before his death, and though he was in ill health at the time, he was able to write, “This is a work that simply swept me away, one of the few works that have been clear to me from the beginning onwards — from the first to the last note.” The listener, on the other hand, is left guessing from the first note, which is played by a solo glockenspiel. A solo flute goes walkabout with the opening theme, and when the bassoon enters, the ambiance turns circusy. A familiar rhythm emerges — surely Shostakovich isn’t suggesting the opening phrases of Rossini’s William Tell Overture? Actually, no, he’s quoting it, in a cheerful volley from the trumpets. We’ll be hearing William Tell often in this short (eight or so minutes) opening Allegretto, along with polyrhythms, a prolation canon, and maybe a hint of the trumpet fanfare from the Mahler Fifth. Shostakovich originally titled this movement “The Toyshop,” and even if he could not have imagined a childhood spent watching The Lone Ranger on American TV, it’s childishly exuberant and cheeky.

The “Adagio — Largo — Adagio — Largo” second movement marks an abrupt transition to adulthood. It begins with a mournful brass chorale pitted against a mournful solo cello before evolving into a funeral march whose chromatic climax evaporates into celesta and vibraphone imitating celesta and then more of that brass chorale and, always, ghostly timpani. The very brief (four minutes) third movement starts with bassoons in parallel fifths and goes on to thumb its nose at conventions of all kinds before ticking to the kind of close familiar from the middle movement of the Shostakovich Fourth. The finale, another longish slow movement, introduces the “Fate” motif from Wagner’s Ring Cycle, followed by what seems an intimation of Tristan und Isolde’s “Sehnsucht” motif, and what we get after that is half march, half dance, as if Shostakovich were channeling the final tableau from Ingmar Bergman’s The Seventh Seal. The composer makes reference to the passacaglia ground from the first movement of his Leningrad Symphony, along with, I suspect, a host of other allusions. The Fate motif persists, and it all ends — if Shostakovich ever really ends — in a “blaze” of celesta, piccolo, triangle, and wood block, what’s been called “a bag of bones.”   

Nelsons gave all this room to unfold without sacrificing intensity. The BSO sounded like a chamber orchestra where every instrument from the toyshop registered as a distinct entity. Nelsons made deadpan comedy out of the way the William Tell references lead nowhere; he brought out, via snare drum, the first movement’s martial side, and Smirnova’s solos provided a link to Gustav Mahler’s unfinished Tenth Symphony (which Shostakovich had been invited to complete). It was a real children’s hour. Then in the second movement, Nelsons balanced a very heavy brass chorale against principal cellist Blaise Déjardin’s sinuous twelve-tone lines. The brass grew murky (not usually a compliment to orchestral playing but here definitely so), Smirnova was heard to good advantage once again, and the theme that the winds eventually announced built to a grinding, horrific (but not ugly) climax before distant trumpets and celesta and wood block and timpani asked what lies beyond.

The second half of the Fifteenth is a variation on the first, right down to the tempo markings: Allegretto for the first and third movements, Adagio for the second and fourth. What functions as a scherzo was from Nelsons a trip through fun-house mirrors, the pace moderate, Smirnova in her solos both spoofy and spooky, the Mahler Tenth again in play. Nelsons’s finale tightroped between dance and march, the repeated quotations of the “Fate” motif serving the same enigmatic function that the William Tell quotations did in the opening movement. At 18 minutes, it was slow but not sleepy; the climax was even more catastrophic than the one in the second movement, and after the “Fate” and “Sehnsucht” quotations returned to offer a kind of recapitulation in a movement that’s more rhapsodic than sonata-form, the “bones” came to afterlife life, Shostakovich’s twinkling, sardonic take on Shakespeare’s “music of the spheres.”

If the opening theme of Rachmaninov’s Third “simply wrote itself,” Nelsons’s Shostakovich No. 15 simply played itself. Neither statement is accurate, of course, but Nelsons’s interpretation attests to what can be accomplished by “simply” listening to the composer.           

Jeffrey Gantz has been writing about music, dance, theater, art, film, and books for the past 35 years, first for the Boston Phoenix and currently for the Boston Globe.