As Marin Alsop prepares to officially take the reins of the Baltimore Symphony this fall, Peter Dobrin takes the measure of her style and work with the orchestra thus far. “A conductor’s work basically falls into two categories: the time in rehearsals resolving ensemble problems such as balance, intonation, the length of notes; and the visual inspiration and tempo manipulations in performance that bring the craft worked out in rehearsal to a level of art. [There is] more work to be done in both areas.”