GORHAM – The University of Southern Maine Composers Ensemble celebrates its 10th anniversary with premieres by USM undergraduates and 10 alumni commissions at 8 p.m. April 17 in Corthell Concert Hall. Admission is free. Of the 26 USM students in the ensemble, seven are working toward a bachelor’s degree in music composition, which being offered for the first time this year at the School of Music. The ensemble will perform Josh Newton’s “There Are No Fruits That Start with X,” in addition to works by USM undergraduates.