LENOX — When you see a soprano on a string quartet program, the only work that comes to mind is Schoenberg's Quartet No. 2.
When you see Renee Fleming on a quartet program, you might think: Isn't she out of her element?
The Emerson String Quartet and the renowned soprano dispelled such notions Wednesday night at Tanglewood by coming up with a real oddity, Egon Wellesz's "Sonnets by Elizabeth Barrett Browning." Schoenberg wasn't entirely absent. Wellesz, an Austrian who settled in England to escape the Nazis, was a student of Schoenberg's, and his settings of five Browning sonnets sounded a good bit like the master's "Pierrot Lunaire" with an amorous twist.
Wellesz was not, however, enough of an Englishman in this 1934 work to set Browning's poems in the original English. He employed a German translation by Rilke.
The dip into Expressionism came in the second of back-to-back Ozawa Hall concerts with which the Emerson launched its 40th-anniversary season. On Tuesday night, the venerable four played all six of Haydn's Opus 76 quartets in a three-hour marathon.
The Emerson has many fine young quartets nipping at its heels but the twin programs showed why it remains among those at the top of the heap. Two of the founding members remain: violinists Eugene Drucker and Philip Setzer, who democratically swap off as first and second. Violist Lawrence Dutton and cellist Paul Watkins round out an ensemble whose immersion in the repertoire shows not in wizardry, but in a sense of inevitability — a sense that, yes, this is how the music should go.
Fleming and the Emerson have been championing the Wellesz work in performance and on a recording. Flanked by Brahms' Quartet No. 2 and Berg's "Lyric Suite," it formed part of a Viennese program here.
It is gallant of Fleming to take up this rarity as she begins phasing out her distinguished career. Her voice was not always easy in the angular jumps that mark the settings of the ornate Victorian poetry, but she clearly wanted the listener to believe in the music as much as she does.
Fleming also sang the text — by Baudelaire, in German translation — that lies behind the last movement of the "Lyric Suite." With its coded messages of love to the married woman Berg coveted, this six-movement work seethes with quiet, inward intensity — a quality that the performance beautifully put across.
The Brahms performance was a cry from the heart. The Emerson superbly tracked Brahms' subtleties of form and mood to get behind sometimes genial surfaces. What emerged were shadowed passions that, like Berg's, betrayed a man's deepest longings.
The six quartets of Haydn's Opus 76 were published as a set but not meant to be performed that way. Each is a gem but all six do make for a long evening. The players deserve some kind of medal for making it through to the end with stamina and conviction that seemed ready for a quartet No. 7. That's more endurance than a lot of the audience showed.
It is possible to play these pieces with a lighter, more mercurial touch. The Emerson, with its burnished tone, went for the depth, the elan, the wit, the constant flow of invention. The variations movements were vividly characterized; the minuets were blessed with a country air; the slow movements sometimes took on an almost Beethoven-like gravity.
The pieces were played in numerical order except for a reversal of the last two. In a way, the maneuver saved the best for last. The first movement's unusual variations, the mournful second movement, the merry chase and jokes of the finale made a lively bedtime story, one that kept you awake.
The program was dedicated to the memory of Joseph Silverstein, the former Boston Symphony concertmaster and a longtime Tanglewood faculty member.