Michael Tilson Thomas could accurately be said to be the populist heir to Leonard Bernstein, a conductor of a major American orchestra who is as determined to make music accessible to the general public as he is to please the usual concertgoing crowd. His latest project with the San Francisco Symphony is a multi-part PBS documentary exploring how music is created, what it means, and who exactly those tuxedo-clad individuals frowning from the stage really are. An extensive web site and a companion radio documentary produced by Minnesota Public Radio will make Keeping Score the largest music/media project ever undertaken by a symphony orchestra.