The name of German writer Wilhelmine von Chézy might have been lost to history had one play, “Rosamunde,” not provided Schubert with a vehicle for one of his many attempts at success as a composer for the stage. By all accounts the play was a debacle in its 1823 debut, yet it lives on, if only as an afterthought, in Schubert’s incidental music.  Bits of the score have popped up over the years on Boston Symphony Orchestra concerts, starting in its very first season, in various configurations. Rarely, though, has it been so thoughtfully programmed as by the German conductor and pianist Christian Zacharias in his current BSO series.  Skipping the overture, Zacharias opened Thursday’s concert with the first Ballet Music, followed by the second and third Entr’actes. This little suite began with a stern minor-key march, a piece seemingly inapt for a dance episode. As it progressed, the music became slower, dreamier, less immediately tethered to reality. But shadows always lurk nearby in Schubert, and even the third Entr’acte — featuring one of the composer’s simplest and most unaffected melodies — carried hints of unease.  Zacharias, who had a score on his music stand all evening yet seemed never to turn a page, led a perfectly shaped performance with gestures that were demonstrative but never exaggerated. He deployed a full complement of strings onstage, including no fewer than nine basses; their prominence heightened the melancholy atmosphere. The rhythms were surprisingly nimble for the ultra-refined sound he achieved.  There is conjecture that the first Entr’acte of “Rosamunde” might have been intended as the finale of Schubert’s Symphony No. 8, the “Unfinished.” Zacharias, though, put it before the symphony on the second half, creating a tempestuous prelude while also recalling the concert’s opening. Barely had the B-major ending of the Entr’acte faded away before the basses and cellos began the grim, lonely melody that begins the “Unfinished.”  In few other Schubert works do darkness and light enact such a pitched struggle, which has made the symphony a kind of emblem of the anguished Romantic imagination. Thursday’s performance was intense and deliberate, painted on an almost Mahlerian scale. It was also slow and in the first movement almost static, robbing some of the climaxes of their power. I wish that the BSO’s glorious wind playing had been able to emerge more clearly from the mass of strings. The Andante, though, was gripping, and its ending has rarely felt so anxious and unresolved.  Before intermission, Zacharias led Mozart’s G-major concerto (K.453) from the keyboard. Here was an airier, more precise sound, and Zacharias’s graceful, restrained style was a model of eloquent dialogue with a reduced orchestra. The slow movement, faultlessly paced and gorgeously played, has an unusually somber episode in an otherwise contented musical expanse — proof that, as in Schubert, the shadows are never all that far away.
The German pianist and conductor Christian Zacharias joined the Boston Symphony Orchestra as the soloist in an elegant Mozart concerto, and the leader of thoughtful, pensive Schubert accounts.