The compulsively contrapuntal mavens of medley--the droll, slightly bitchy pianist-arranger Robin Field and his younger, cockier Irish-tenor partner Bill "I Don't Do Keyboards" Daugherty--are back for a limited engagement with their ever-expanding collection of classic songs and original novelty items. What these two do with a tune or two--make that two dozen, or is it 200?--is almost indecently innovative: their highly theatrical rearrangement and juxtaposition of master and minor pieces from the great days of big-band jazz and Broadway shows make for hilarious and often brilliant entertainment. In this evening-length revue the popular New York team focuses on two interrelated themes: "Fantasies" (which can, and will, range from tales of romantic adventure to Daugherty's screamingly funny imitation of Donald Duck) and "The Big City," with selections ranging from Guys and Dolls numbers and the Duke Ellington canon to the rarely heard "Tenement Symphony" from the Marx Brothers movie The Big Store. Expect (and, if you don't hear it, demand) their wonderfully funny, musically virtuosic rendition of Gershwin's Rhapsody in Blue--complete with irreverent lyrics describing the composition's composition--as well as a sampling of special material from the team's new recording called, as it happens, Special Material. For fans of musical comedy that's offbeat and on the mark, this is a must-see show. Halsted Theatre Centre, 2700 N. Halsted, 348-0110. Opens Friday, November 27, 7:30 PM. Through December 6: Wednesdays- Fridays, 8: 15 PM; Saturdays, 6:30 and 9:15 PM; Sundays, 3:30 and 7 PM. $15-$26.50.