David Robertson has officially arrived as the new music director of the Saint Louis Symphony, and the city may never have seen a conductor more eager to get started. “On Monday, Robertson threw out the first ball at the Cardinals game… On Tuesday, he heard auditions. On Wednesday, he held his first rehearsal as music director, and then charmed the audience at a ‘town hall’ meeting in [suburban] Des Peres.” Robertson’s biggest task may be restoring the orchestra to its place among the top American ensembles after years of crippling deficits, high-profile labor disputes, and organizational malaise.