Unusual for relative newcomers, the nine-voiced Chicago a Cappella command a repertoire that stretches from early Renaissance to late contempo. While the group excels in just about every category–its sharp ear for early music will be demonstrated later this year when its collection of Palestrina Christmas music is released on Centaur–it has a knack for the American vernacular. So this season’s closer consisting of assorted American folk anthems and gospels from the early 1800s on could be a rousing, heartfelt affair built on solid, precise singing. Foremost in the thick anthology is “Birth of Soul, Part I,” a brand-new composition by north-sider Peter Saltzman. The first–and stand-alone–movement from a larger work in progress that intends to cast Judaic spiritualism in essentially African-American musical idioms, this 15-minute piece is a pleasingly cast medley of peppy and devotional tunes based on familiar folksy melodies. Saltzman, a pianist who was trained at the Eastman School but left the academic world out of frustration with its doctrinaire ways, shows admirable sensitivity to vocal contours. His sincerity in reminding Jews and blacks of their shared religious fervor is exemplified by his deft take on “Go Down, Moses,” filled with off-pitch curlicues. Also premiering is an arrangement of “Been Down Into the Sea,” from local baritone Wayland Rogers. Jonathan Miller, the group’s founder, conducts. Saturday, 8 PM, Unity Temple, 875 Lake, Oak Park. Sunday, 7:30 PM, Church of St. Luke, 1500 W. Belmont. 708-383-7599 or 800-746-4969. TED SHEN