What kind of conductor will replace Leonard Slatkin as music director of the National Symphony? Tim Page writes that it’s instructive to look at the orchestra’s history. “It is too early to speculate with much authority on who will become the sixth music director of the National Symphony Orchestra. Slatkin’s contract runs for another three seasons (although he is thought to be actively pursuing other jobs, especially Daniel Barenboim’s soon-to-be-vacated position with the Chicago Symphony Orchestra), and the search process is still in its beginning stages.”