This weekend's Indianapolis Symphony Orchestra program proves that orchestra concerts aren't totally predictable.

ISO Music Director Mario Venzago was scheduled to conduct a program dominated by music of Robert Schumann, but Venzago canceled because of an unspecified illness.

James Gaffigan, the San Francisco Symphony Orchestra's associate conductor, is standing in, and after intermission, he substituted Antonin Dvorak's Symphony No. 8 for the originally scheduled Schumann Fourth.

Add the fact that Canadian violinist Leila Josefowicz gave an outstanding performance of British composer Oliver Knussen's challenging, little-known Violin Concerto from 2002, and one might call the program an evening of surprises.

Gaffigan's performance Friday night at Hilbert Circle Theatre summoned a big, muscular sound from the orchestra. That seemed evident even after the initial strains of the opener, Schumann's "Overture, Scherzo and Finale."

Both pieces on the concert's first half (the Schumann and the Knussen Concerto) contain three movements without interruption.

Gaffigan and the orchestra contrasted each movement of the Schumann in detail. They produced a full-bodied sound in the overture, getting lighter and quieter in the scherzo. The finale began with crisp articulation, moving on to sustained phrasing in the chorale.

The Knussen Concerto evolved from the opening "Recitative" to "Aria" and then a concluding "Gigue." The concerto, originally composed for Pinchas Zukerman, is dramatic from start to finish, and a virtuosic tour de force, containing passages in the violin's extreme high and low registers, fast bowing and complex rhythms.

Movements of the concerto did not seem as distinctive in this case, making me wonder if they might be more impressive with breaks between them. Josefowicz seemed to enjoy the theatricalicality of the work and easily handled technical demands.

Gaffigan's interpretation of the Dvorak Eighth included a wonderfully controlled string sound in the second movement, but the conductor's penchant for a big sound and sweeping phrases dominated the symphony, especially in the outer movements.