The news stories about the Pittsburgh Symphony’s new artistic leadership model made copious use of the term “triumvirate.” But, says Andrew Druckenbrod, the PSO’s plan is far from the idea of a three-headed boss, and that’s a good thing, given the clashes of ego that could be involved in such an arrangement. “In truth, no one is succeeding Mariss Jansons as music director — not [Sir Andrew] Davis, not all three of the conductors. That’s the heart of the revolution of the PSO’s announcement: The changed relationship between an artistic leader and the orchestra that gives the musicians and staff more power in deciding the future of the group.”