Choreographer Liz Lerman is a "call and response" kind of artist. Her dances -- many of them political, provocative and studded with familiar words and gestures -- seem to cry out for reaction on the part of the spectator. Hence the "Evenings of Exchange" series.

These informal performances, introduced several years back, provide the perfect environment for this "call and response" process to unfold. Finished works and works in progress get equal time, discussion follows and artists often solicit advice from the audience. Saturday night, in the chilly confines of Mount Vernon College's Hand Chapel, Lerman presented two recent works -- "Atomic Priests: Coming Attractions" and "Sketches From Memory" -- and previewed a brand-new piece, "Atomic Priests: The Feature," which premieres Thursday at Manhattan's Dance Theater Workshop.

It was my first look at all three works, and I came away both enlightened and frustrated (unlike the majority of the audience, which reacted more favorably). In both the first and last pieces, Lerman confronts the issue of nuclear waste, but in vastly different ways. In the pithy, condemnatory "Atomic Priests: Coming Attractions," she blends material from reports by the Department of Energy with an alternately humorous and frightening barrage of gestures, postures and dance interactions between five members of a dunderheaded task force. The result is classic Lerman: a salient message conveyed in an accessible and thought-provoking way.

"Atomic Priests: The Feature," which explores the aftereffects (10,000 years hence) of the task force recommendations, treats its subject in a far more ponderous manner. The message is blurred, the futuristic movement, music and costumes come off as sophomoric and nonspecific. Even the text -- usually Lerman's forte -- seemed too wordy, too larded with half-baked myths, legends and a thousand and one cutesy alliterations. The call to action of the first work turned into an incoherent rant in the second.

Sandwiched between these timely creations was the mysterious, evocative "Sketches From Memory." A woman lectures coyly on the wonders of tropical fish. An older woman and a younger man dance a languid, romantic duet. Six women of varying ages gallivant and goof in '50s-style prom dresses. A young man forces his hospitalized father into an angry and eventually loving meeting. What these scenes have to do with one another is anybody's guess, yet their collective power is undeniable. It is as if one is experiencing a particularly potent dream.

The performers, members of Liz Lerman/Exchange and the Dancers of the Third Age, brought Lerman's concerns and dreams to splendid life.