Concertante di Chicago, an unusual chamber ensemble in that it performs without a conductor, seems to thrive on the kind of engrossing esprit de corps characteristic of the best string quartets. It also typically brings a strong sense of musical coherence and continuity to its concerts--take the season opener. The four pieces are each eminent examples of Viennese classicism by themselves; yet performed back-to-back they'll certainly provide a heightened appreciation of the famous style's turning points. Haydn's Symphony no. 88, one of the more than 20 written by the prolific kapellmeister during the 1780s, is melodious, witty, and utterly charming in its artful simplicity. Beethoven's Third Piano Concerto, of course, is often cited in textbooks as a ground breaker, the first time piano and the orchestra had been cast as dramatis personae in an edgily psychological symphonic drama. (Both works are usually performed by full-size orchestras; it remains to be seen whether a chamber orchestra can bring out their dramatic force.) The third and fourth pieces are by Mozart: the Overture to Cosi fan tutte and a concert aria (to be sung by soprano Elizabeth Futral). The soloist in the Beethoven concerto is Carmen Or, who defected from the Soviet Union as a teenager and is now a faculty member at Northwestern University. Sunday, 3 PM, concert hall, DePaul University, 800 W. Belden; 993-7887.