SWEET NOTES, SOUR NOTES

When Grandpa Zayde takes David to hear concert violinist Mischa Elman, David is so enthralled that he begs his parents for a violin so that he, too, can make it sing. Eventually, an instrument is rented and lessons with imperious Madame Markov begin. Predictably, more practice and patience are required than David had imagined, but his perseverance pays off in time to cheer his sick grandfather (who was never able to realize his own dream of playing the violin) by playing ``Twinkle, Twinkle, Little Star.'' The simple story, depicting a nice, traditional Jewish family of the 20's, reads like an expanded picture book; still, the short chapters, each with its somber but evocative full-page b&w illustration, add up to a pleasant—if quiet— beginning chapter book. (Fiction. 7-10)