The results had polish and energy. Michael Tilson Thomas, stepping down as music director here after 25 years, has built an ensemble that plays with clean, versatile shine. (It can feel, in its agreeably open versatility, not so far from the Los Angeles Philharmonic.)
The San Francisco string sound, in particular, is glistening yet full-bodied, never hysterical but with a lovely glitter to the tone. Russ deLuna played the crucial English horn solo in Sibelius’s “Swan of Tuonela” movement with self-effacing eloquence. Indeed, solos throughout the concert were alert yet unshowy, always with a sense that the big picture was more important than stealing a star moment.
Mr. Salonen conducted the premiere of “Metacosmos” in April with the New York Philharmonic, and it makes a clever companion to “Also Sprach Zarathustra.” Both begin with the same low growl — though, as Ms. Thorvaldsdottir’s orchestra begins to rouse itself into a Strauss-style fanfare, it dolefully falls apart. This cycle of expansion and collapse defines the piece; lush, even cinematic gestures are pulled at by sickly downward moans.
This was a powerful, logical “Zarathustra,” lithe and bombast-avoidant in a thrillingly controlled opening and airy in the lilting passages later on. Mr. Salonen’s Sibelius was lean and fevered.
This isn’t an orchestra that does spectacular soft atmosphere, but moments like the stillness of the second movement, “Lemminkäinen in Tuonela,” when the barest shiver of violins is frosted by the barest shiver of rat-a-tat drum, were finely controlled. It was a performance not of effects or jarring contrasts, but of sustained force and focus.
The classical field is now waiting to see what Mr. Salonen will do in his career’s full maturity. He has announced a benevolent little think-tank army of artists who will be helping him, including Nico Muhly, Esperanza Spalding and Julia Bullock, and their plans will germinate through next year, as the orchestra turns to celebrating Mr. Thomas’s final season.