The later works of Johann Sebastian Bach are seldom heard on the sort of instruments for which Bach wrote them. The period-instrument debate goes back and forth (would Bach have preferred modern instruments if he’d heard them?), but even those who prefer a modern sound can gain new insights from listening to old sonorities. Chicago Baroque Ensemble is presenting a program that includes the local period-instrument premiere of the Concerto in D Major for Harpsichord as well as the Sonata in G Major for Viola da Gamba and Harpsichord and the Suite no. 2 in B Minor for Flute and Strings. The sterling group of performers includes harpsichordist David Schrader, flutist Anita Miller-Rieder, violinists Jeri-Lou Zike and Jennifer Roig-Francoli, violist Melissa Trier-Kirk, cellist John Mark Rozendaal, and contrabassist Jerry Fuller–all playing reproductions of authentic Baroque instruments, from a wooden flute to gut-strung violins. Sunday, 3 PM, Block Gallery, North- western University, 1967 South Campus Dr., Evanston; 708-491-4852.