The intrepid ensemble shines a light on the sole string quartet written by Fanny Mendelssohn, an active 19th century composer whose works were largely unrecognized during her lifetime. Jeremy Denk joins the group for the second half with Schumann’s ebullient piano quintet, one of the very first works to pair the traditional string quartet configuration with piano. Dedicated to Clara Schumann, the fiendishly difficult piano part was first performed by Fanny Mendelssohn’s brother, Felix, when Clara fell ill, though she was at the keyboard for the first public performance a month later.