An orchestra's fourth, or utility, trumpet is rarely asked to perform a concerto, but the level of talent today is so high that many nonprincipals are more than capable of accomplished solo playing. As the CSO's fourth trumpet for nearly two seasons, Tage Larsen has turned in polished, commanding performances regardless of where he's been sitting. Like any musician who wins a CSO audition, he has flawless technique, but there's a thoughtful quality to his sound not always heard from brass players. In this concert with the Chicago Sinfonietta he'll perform Haydn's Trumpet Concerto, a work whose revolutionary qualities aren't as obvious now as they were when Haydn wrote it. A recent innovation in the trumpet's design had made it possible for a virtuoso to do something unheard of--play an entire major scale in the middle and lower registers. Haydn wrote the concerto to showcase this new capability, and audiences at the premiere must have been amazed. This program also includes Ibert's farcical Divertissement, which was adapted from music for a stage comedy. He wittily underlines the laughs, sending up both Strauss's "The Blue Danube" and Mendelssohn's "Wedding March"--national rivalries have long been predictable laugh getters--and the whole thing sounds like well-crafted circus music. Minjeong Lee, whom I haven't heard, plays Tchaikovsky's Piano Concerto no. 1. Paul Freeman conducts. Sunday, April 25, 2:30 PM, Dominican University, 7900 W. Division, River Forest, and Monday, April 26, 7:30 PM, Orchestra Hall, Symphony Center, 220 S. Michigan; 312-236-3681.