Of all the youngsters stealing the jazz spotlight these days--a list that starts with Roy Hargrove, Benny Green, and Philip Harper, and that Wynton Marsalis has already outgrown at the advanced age of almost 29--Christopher Hollyday could well turn out to be the most important. He's only 20, but facts are facts. His recently released album, On Course, is only his second for the Novus label, but it's a wild leap past the first, showcasing his own compositions and the crackerjack quartet he brings to town next week. Where his fellow kiddie-korps saxists have looked to relatively predictable models, such as Coltrane and Shorter, Hollyday has grabbed the biting tone, the tough and earthy harmonies, and the crackling intensity of altoist Jackie McLean. In the 50s, McLean (who is still active) helped push the envelope and prepare the way for Ornette Coleman; Hollyday clearly grasps this brashly adventurous side of McLean's well-schooled talent, and seems intent on riding it toward his own stylistic independence. But past all that, he's just a bitch of a player--an assessment that is not colored by his age: there are plenty of guys out there with twice the training and experience and half the musical insight. (Hollyday will play a 25-minute set opening for Harry Connick Jr., which is understandable: if I were peddling Connick's brand of jazz-based. nostalgia, I wouldn't want this red-hot alto man out there very long, either.) Tuesday, 8 PM, pavilion, Ravinia Festival, Green Bay and Lake Cook Rds., Highland Park; 728-4642.