The libretto of Engelbert Humperdinck's Hansel and Gretel (by Humperdinck's sister) is unassuming and wryly observant, but it is the beauty and simplicity of the music that ensures this one-of-a-kind fairy tale opera's status as a timeless classic. Originally intended as an antidote to Pucciniesque verismo, the frolicsome, shimmering score for the story of the brother and sister trapped by a witch in her gingerbread house serves as a vivid and refreshing reminder that childhood traumas can be infinitely more fascinating and meaningful than adult ones. In this fully staged production (a rare treat), the lead roles are sung (in English) by Susan Hofflander (Hansel), Susan Foster (Gretel), and Phyllis Pancella (Mother/Witch), all members of the excellent Lyric Opera Center for American Artists. Directing them and the University of Chicago Symphony Orchestra is Barbara Schubert, one of our best (if unheralded) young conductors. Tonight and Saturday, 8 PM, Hutchinson Courtyard, University of Chicago, 57th and University; 702-7300.