Michael Tilson Thomas' five-year campaign to bring some new blood into Davies Hall is beginning to work. San Francisco Symphony marketing director Michelle Prisk says the most recent figures available for the average age of season subscribers is 53 and single-ticket purchasers are younger, although there are no similarly reliable statistics for that group. Now 53 is not only younger than the average age for Deadheads (brought into the symphonic fold by MTT early in his career here, in a joint concert with the surviving Grateful Dead), but it is also at the low end of the national range of "between 50 and 60." The latest study by the National Endowment for the Arts found the prime audience for classical music was born between 1936 and 1945, and individual orchestra studies often report 60 or close to it. The San Francisco figures represent a drop of about four years since MTT's arrival. Janos Gereben/SF, CA [log in to unmask]