The oratorio “La Passion de Simone,” performed last week at the Rose Theater, had as its sole props a writing desk and a richly burnished, framed door. While the audience was being seated, the City of Birmingham Symphony Orchestra filtered in among dozens of chairs and music stands, and those spare devices seemed a mite inconsequential. But director Peter Sellars hadn’t left any tricks up his sleeve for the 90-minute work he and the Mostly Mozart Festival’s composer in residence, Kaija Saariaho, created in 2006. As applause greeted the soprano Dawn Upshaw, the dancer Michael Schumacher, and the Finnish conductor Susanna Mälkki, it turned out that the rewarding surprises of the evening were, along with the furniture, already onstage: the CBSO musicians and the London Voices chorus, who’d been seated before the orchestra entered in the boxes at the back of the stage.

Ms. Upshaw, as an unnamed character seeking guidance from the mid-20th-century martyr Simone Weil while re-enacting situations in the French Jewish philosopher and mystic’s short life, brought her devotion and intelligence to bear throughout “La Passion.” (It is the third panel of a trilogy by Ms. Saariaho, along with the praised operas “L’amour de Loin” and “Adriana Mater,” all with librettos by the Palestinian author Amin Maalouf.) In an initial phrase sung directly to the onstage door, Ms. Upshaw imparted a compelling transmission of text and feeling, while in a later lyric, “Only in this flame …” (as near to an aria as Ms. Saariaho’s tightly wound score allows), her penetrating delicacy was superb. She was repeatedly approached, readjusted, and then left by Mr. Schumacher. Both singers wore Martin Pakledinaz’s costumes, which suggested classy institutional drab. Mr. Sellars’s staging traversed a palimpsest of religious observances, including Shiva poses struck between Mr. Schumacher’s bouts of martial movement and a position in which Mr. Schumacher’s hands were balled above Ms. Upshaw’s head as if he were a sage milking the heavens.

Ms. Mälkki activated vast instrumentation that seldom played forcefully, cleaving instead to a sometimes tidal, sometimes astral spectrum rife with tactics of cut and flow attributable to the composer’s early work in electronic and tape music. As with Bach’s Matthew or John passions, “La Passion” presents meditations on something dramatic, not the drama itself. Though Ms. Upshaw sometimes appeared to play Ms. Weil, and though some gestures did not enhance the musical atmosphere — the cover of a Weil book, displayed like an amulet; a pandering kiss that began the eighth movement’s haunting orchestral passage — nothing distracted.

The CBSO was at Ms. Mälkki’s beck and call in an acute, nuanced performance. Marimbas rolled in the midst of propulsive orchestral luxuriance, then the whole would brake with slurring, eliding diminishments. At other junctures, an oboe introduced the seventh movement’s “When you left the factory … .” A shard of a gypsy violin played off a sustained pitch that seemed to come from nowhere and everywhere in the orchestra, while elsewhere the strings bowed up harshly near the bridge as vibraphones loped. Meanwhile the London Voices, from their aerie on the Rose Theater’s rear wall, holding faintly illuminated librettos, served both as observer and interlocutor for Ms. Upshaw and the prerecorded voice of Dominique Blanc reciting from Ms. Weil’s philosophy. The chorus’s presence, in a model of theatrical simplicity, spurred the captivating music of “La Passion” while functioning as the visual foundation of an allegorical stratigraphy, as if the oratorio were an Old Master tableau vivant or a Peter Greenaway storyboard. “La Passion” is dense and adult, and resolves in a religious ultimatum as refined as the eternal recurrence: “Nothing that exists is worthy of absolute love / so we must love that which does not exist.” In the oratorio’s concluding stations, the door goes blood-red, and it is to the credit of all involved that the final gesture, as Ms. Upshaw pulled that door to, felt so ambiguous, and so right.

Last week’s focus on Ms. Saariaho’s work included her cello concerto “Notes on Light,” played by Anssi Karttunen with Ms. Mälkki conducting the CBSO in another outstanding performance. (Ondine releases the premiere CD of the concerto next month.) An evening of Ms. Saariaho’s chamber pieces in the Kaplan Penthouse on Friday night, mixed with pieces by Debussy, felt largely like experiments, though the pianist Tuija Hakkila was utterly convincing in Ms. Saariaho’s “Prelude,” leaving the audience holding its collective breath. This Thursday at Avery Fisher Hall, the Emerson String Quartet will present the premiere of Ms. Saariaho’s “Terra Memoria,” on a program with Mozart and Schubert.