ROCKPORT — In some quarters, one can detect a quiet condescension toward the Polish composer Krzysztof Penderecki for having turned his back on his futuristic works of the 1950s and ’60s and embraced a more traditional aesthetic. But this superficial judgment crumbles on listening closely to some of Penderecki’s post-avant-garde works, especially the chamber music written since the 1990s.
Consider his Third String Quartet, “Leaves of an Unwritten Diary,” which the Shanghai Quartet commissioned, premiered in 2008, and played on Saturday in the first of two concerts at the Rockport Chamber Music Festival. Its sections are tonally centered and melodically rich. So, sure, call it conservative. But its textures — now caustic and astringent, now dense and motoric — are more internally varied than in most of Penderecki’s earlier works, and the economical use of thematic material is masterfully hidden beneath jagged surfaces. Innovation is not so simple a matter.