So far the early signs point to a more progressive, more eclectic era for the CSO under Solti successor Daniel Barenboim. This week on a different CSO program, Pierre Boulez (represented by a key work, Notations) is being accorded due recognition as one of the seminal figures of 20th-century music. And this program premieres a pair of CSO commissions. Ellen Taafe Zwillich’s Concerto for Bass Trombone, Strings, Timpani, and Cymbals, as the unwieldy title suggests, is a showpiece for the trombone: it was tailored specifically to CSO player Charles Vernon. Zwilich, who was both the first woman to obtain a PhD in composition from the Juilliard School and the first woman to win a Pulitzer Prize in music (1983), is a first-rate craftsman. Her music is sometimes too straitlaced for its own good, but this concerto may allow her to loosen up a bit, to indulge in some individualistic touches. Last Voyage, by LaGrange resident and Roosevelt University Alum Stephen Kowalsky, was chosen by Barenboim as the winner of the CSO-sponsored Illinois Composer’s Competition. Based on the real-life incident of a freighter’s disappearance in an ice storm on Lake Superior in 1927, this ten-minute work depicts, I’m told, the emotions of the ship’s mascot as the disaster unfolds. This may be the most perverse canine narrator since Gertrude Stein’s dog. Also on the program: Brahms’s Symphony no. 1. Tuesday, 7:30, Thursday, 8 PM, and next Friday, May 3, 1:30 PM, Orchestra Hall, 220 S. Michigan; 435-6666 or 435-8122.