The siblings Felix and Fanny Mendelssohn were both precocious musicians as children, although Fanny’s career was stymied by the barriers confronting professional women in 19th-century society. She nonetheless composed more than 400 pieces, and the String Quartet in E-Flat Major is one of the most substantial. The Quatuor Ébène gives it a near-definitive performance, poignant in the third movement “Romanze,” fiery and ebullient in the optimistic finale. Fanny’s quartet is flanked by two of Felix’s, including No. 6 in F Minor, a work written in the emotional aftermath of Fanny’s death, aged 41, in 1847. The raw anguish of the opening movement is vividly captured in the Quatuor Ébène’s edge-of-seat performance, and they convey the combination of heartbreak and gentle consolation to perfection in the “Adagio.” For technical exactitude and emotional commitment, few quartets can match the Quatuor Ébène in these Mendelssohn family pieces.