Some of the best performances I've seen in Chicago theater during the past five years--the most nuanced, the most focused, the most subtly expressive, the funniest and most touching--have come from Ross Lehman. In roles ranging from a sexual revolutionary headed for a breakdown in Next Theatre's The Normal Heart to an old Roman slave in the Goodman's A Funny Thing Happened on the Way to the Forum to an egotistical villain in Shakespeare Repertory's The Tale of Cymbeline, Lehman has consistently displayed a rare mix of passion, puckish humor, economy, and illumination. Possessed of a light, warm baritone, he's particularly gifted as a dramatic singer; he reaches listeners not by selling a song but by living within it. Except for a few pricey benefits around town, he hasn't spent much time in intimate cabaret settings, so it will be interesting to see him use his night off from playing the lead in Drury Lane Oakbrook Terrace's Damn Yankees to participate in the Royal-George's March cabaret festival. His program will consist mostly of jazz standards of the 1930s and '40s, with some folk tunes; but since he'll be accompanied by pianist Mark Weston, he'll likely perform some of the songs he and Weston wrote for their charming musical version of O. Henry's "The Gift of the Magi." Tuesday, Ruggles Cabaret, Royal-George Theatre, 1641 N. Halsted; 988-9000 or 902-1500.