One sign that chamber music still thrives--albeit modestly--is the popular series at the North Park College that has been drawing residents in the city's northwestern neighborhoods. Another sign is the number of young conservatory graduates still willing to collaborate in string quartets. The Rackham was formed only a year and a half ago at the University of Michigan, and it has already embarked on the requisite course that may eventually propel it to the top of the chamber-music world. It's won a clutch of prizes and its twentysomething members--violinists Leonra-Marya Anop and Laurel Butler, violist Kenneth Martison, and cellist Andrew Ruben--are linked up with prestigious (and influential) mentors. One such guardian angel is Richard Young, violist with the Vermeer Quartet. Nor surprisingly, the Rackham plays like a junior-league Vermeer. Its repertoire, admittedly, is quite thin by comparison, but in terms of precision and ardor, the foursome can be quite impressive. Like the Vermeer, there's a tendency to accentuate the romantic, to swoon over melodic lines. This aspect may become evident in Rackham's interpretation of Mendelssohn's airy Quintet in B-flat at tonight's recital, especially since Young will participate as the second viola. Venturing into the Baroque era, the youngsters will team up with Marc Johnson, the Vermeer's cellist, to play Boccherini's delectable Quintet in C. In stark contrast, Bartok wrote quartets that demanded emotional intensity and conviction, and it will be interesting to see if the Rackham can match the Vermeer in its delivery of his Fourth Quartet. Friday, 8:15 PM, Lecture Hall Auditorium, North Park College, 3225 W. Foster; 583-2700, ext. 4300.