The Chicago String Ensemble’s “American Night” concert, yet another example of the group’s thoughtful, exploratory programming, turns out to be a posthumous salute to Aaron Copland, the doyen of American music who died last month. Originally devised to honor Copland’s 90th birthday and Samuel Barber’s 80th, the program includes seldom-performed pieces by both masters. The Copland work, Quiet City (1940), is obscure compared to its popular sibling Billy the Kid, but its spritely syncopated depiction of urban hurly-burly definitely warrants another hearing. The same can be said of Barber’s Capricorn Concerto (1944), nowhere near as celebrated and beloved as his Adagio for Strings but a further validation of his flair for orchestrating the strings. Also featured will be local premieres of works by three younger, active composers whose styles are radically different and whose places in American music have yet to be determined. Alvin Singleton is an African American based in Atlanta; he’s represented by An Idea Is a Piece of Cloth (1988), said to be jazz for strings. New Yorker Sheila Silver’s Shirat Sarah (1987), inspired by a pilgrimage to Jerusalem, universalizes the anxieties and joys of late motherhood as experienced by the biblical Sarah, wife of Abraham. Also strongly personal is Shards of Memories, a fresh-off-the-press piece for alto flute and strings written by local boy David Zabriskie for the CSE and flutist Lyon Leifer: according to the composer, it’s about recent events in Zabriskie’s life, including the lingering death by cancer of the daughter of CSE maestro Alan Heatherington. Both Silver and Zabriskie will be on hand for the hour before the performance at Saint Paul’s to discuss their works. Tonight, 8 PM, Saint Paul’s United Church of Christ, 2335 N. Orchard; 332-0567. Saturday, 8 PM, Hammerschmidt Chapel, Elmhurst College, 190 Prospect, Elmhurst; 332-0567. Sunday, 3:3 0 PM, Schaumburg Prairie Center for the Arts, 201 Schaumburg Ct., Schaumburg; 332-0567 or 708-894-3600.