It’s every orchestra manager’s nightmare: just a few days before the scheduled performance of a virtuoso showpiece the soloist gets sick and a replacement must be found. And not just any replacement; it has to be someone who knows the piece and has the chops to pull it off.

The word “substitute” often has pejorative undertones, but this weekend at Powell Hall defies them.

David Robertson's on-stage introduction to Philippe Manoury's "Synapse", for violine and orchestra, made more sense than the composer's own description, which fluttered about such terms as "blocks", "formulas" and "specific grammar" without really explaining their true meaning. However, Robertson's substantial personal charisma seemed insufficient to make such a piece palatable to what was easily the sparsest audience in memory at a St. Louis Symphony concert.