The Chicago Jazz Ensemble–a superlative jazz repertory orchestra–regularly peppers its concerts with music from jazz’s misty past, as well as newer works by its director, William Russo. You’ll find both on this program, but it all plays second fiddle to a rare performance of Duke Ellington’s lively and moving New Orleans Suite. In fact, as far as anyone can tell, this will be only the second public performance of the nine-movement work–and the first did not come under Ellington’s baton. The jazz impresario George Wein commissioned Ellington to compose this work for the 1970 New Orleans Jazz Festival (a then-small local event that has grown into today’s behemoth, the Jazz & Heritage Festival); Ellington wrote five movements with such atmospheric titles as “Second Line” and “Bourbon Street Jingling Jollies” and premiered his work at the festival in April. Then in the following three weeks he wrote another four movements–musical “Portraits” of Louis Armstrong, Mahalia Jackson, the New Orleans soprano-sax pioneer Sidney Bechet, and the former Ellington bassist Wellman Braud (himself a New Orleans native)–to turn the suite into a symphonic-length work. But the Ellington Orchestra never performed the entire piece, not in public or even in the studio: the band recorded the “portraits” about two weeks after the first taping session. (In the interim, the alto saxist Johnny Hodges–the most important and distinctive of Ellington’s longtime sidemen–had died, irrevocably lessening the band’s power.) The Chicago Jazz Ensemble has previously proved its mastery of Ellington’s repertoire; for this single performance they’ve enlisted Chicago Symphony clarinetist Larry Combs and the spectacular piano tickler John Weber to join such surefire soloists as Orbert Davis and Rex Richardson (trumpets), Ari Brown (saxophone), and Audrey Morrison (trombone). Saturday, 8 PM, Mandel Hall, University of Chicago, 1131 E. 57th; 461-9708 or 663-9462.