Founded in New York City in 1972 by cellist Julian Fifer, the Orpheus Chamber Orchestra has followed the standard European orchestral model of being entirely self-governing; that is, rather than having an outside conductor or music director or manager dictate repertoire, programming, rehearsal techniques, or interpretive decisions, the orchestra members vote. The 26-member orchestra, which both rehearses and performs without a conductor, has chosen a bold repertoire for its present tour, which includes the legendary Austrian pianist Alfred Brendel playing the Mozart Piano Concerto no. 19 in F Major (K. 459), which by itself would make this concert worth hearing. More Mozart will be represented by the Divertimento in E-flat Major (K. 113). Mozart’s music, which was written before the advent of the stand-up conductor, can sail along pretty smoothly without one if the musicians are used to playing that style of music together and listen to each other very carefully. What will really be interesting is to see how the group will tackle Wagner’s Siegfried Idyll and Schoenberg’s Chamber Symphony no. 1 without a conductor. The evening promises to be either a total mess or an eye-opening revelation, but I’m betting on the latter. Sunday, 7:30 PM, Pick-Staiger Concert Hall, Northwestern University, 1977 Sheridan, Evanston; 491-5441.