Maurice Ravel's string quartet was mostly dismissed as a failure by his teacher, by a prestigious contest and by music critics in Paris. But ever since Claude Debussy gave an enthusiastic thumbs up, Ravel's one and only string quartet has become a staple of the chamber music repertoire. Also we hear a double piano concerto by J.S. Bach that would have been played in a busy, bustling coffeehouse in Leipzig. On Tuesday's Performance Today.