A critic once described the first encounter with the Chiaroscuro Quartet as a “shock for the ears.” Over the past two decades, the group has come to be regarded as the leading string quartet for historically informed performance practice, and with their adventurous interpretations the four musicians transform even familiar repertoire classics into unexpected discoveries. A fixture of past Pierre Boulez Saal seasons, the ensemble has chosen works by Haydn, Beethoven, and Schubert for its latest program.