Porchlight Theatre, which has emerged as one of Chicago's best small non-Equity companies over the past couple of years, closes its superb staging of Merrily We Roll Along this weekend just in time to gear up for another opening next week. As part of the Theater on the Lake's summer season, the troupe is remounting its 1999 production of Falsettos, William Finn and James Lapine's funny, moving pop opera about a gay man named Marvin and his tortuous efforts to make peace with himself, his boyfriend, his former wife, and his adolescent son. Set in the late 70s and early 80s, the work finds Marvin coping with his own neuroses, his kid's impending bar mitzvah, his ex's remarriage--to Marvin's shrink, yet--and his lover's diagnosis with AIDS. In the original run (which opened for a two-month engagement and ended up playing 27 weeks), director L. Walter Stearns and his cast proved that musicals are about acting as much as singing and dancing: the strong voices and quirky choreography were bolstered by expressive, intelligent, carefully nuanced characterizations. A few of the cast members are different this time around, but the keen insight brought to the material by Stearns and musical director Eugene Dizon should, if anything, have deepened. And the biggest drawback in last year's production at the Athenaeum Theatre--troublesome sight lines caused by an elevated stage that ran down the middle of the room, forcing front-row viewers on either side to crane their necks upward--should be solved by the lakefront auditorium's more traditional configuration. Theater on the Lake, Fullerton and Lake Shore Dr., Chicago, 312-742-7994. Opens Wednesday, June 28, 8 PM. Through July 2: Thursday-Saturday, 8 PM; Sunday, 4 PM. $10.