Simon Preston is sort of England's unofficial organist laureate. He boasts the kind of credentials that bespeak pedigree and establishment: graduate of Cambridge University, longtime organist at Westminster Abbey, head of Christ Church Choir at Oxford, music planner for the wedding of Prince Andrew, et cetera. But this kind of background doesn't mean he's dull and academic-minded. On the contrary--those familiar with his numerous recordings over the past three decades know he's been an ardent champion of the oeuvre of Olivier Messiaen (also an exciting organist) and one of the world's best all-around organ emissaries and choral conductors. In this rare Chicago recital, the first in a series of outreach events sponsored by Music of the Baroque in conjunction with Northwestern's School of Music, Preston has slated a potpourri of organ masterpieces through the ages: a Handel concerto, a prelude and a fugue by Bach, Mozart's Fantasia in F Minor, and an Elgar sonata. Saturday, 8 PM, Alice Millar Chapel, Northwestern University, 1870 Sheridan, Evanston; 663-1900 or 708-491-5441.