When Ann and Bob were typical California kids filling notebooks with musical sketches, little did they realize how that would eventually turn out. Ann never stopped composing and her brother Bob became a major epidemiologist, vet, violinist, and rowing enthusias. When he died at the age of 55, it was time to bring all those threads together in one musical homage. Ann Milikan's ''Milikan Symphony'' - recorded here by th eBoston Modern Orchestra Project, directed by Gil Rose with Jennifer Curtis as a violin solost - is more than a loving tribute to her sibling; it is a research project in its own right, worthy of its brilliant dedicatee. Each movement focuses on one aspect of Dr. Robert C. Milikan's life: science, animals, rowing, and violin. As a scientist, ''Dr. Milikan and his colleagues conducted three waves of this country's groundbreaking longitudinal study of breast cancer in African-American and Caucasian women,'' said Shelley Earp, MD, director of UNC Lineberger. ''Through th eCarolina Breast Cancer St