Amy Alt, one of Jan Bartoszek’s dancers, said during an open rehearsal that she had some misgivings when she first heard about the choreographer’s new piece: since it was about midlife and focused on the cha-cha, Alt imagined anguished married couples dancing around suburban living rooms. But as one observer at the rehearsal remarked, “If this is middle age, I can’t wait!” In fact Bartoszek’s Viva is far from depressing or stodgy: it features some of the most exuberant yet natural partnering I’ve seen in a long time–and Bartoszek doesn’t stop at duets. The Hedwig dancers looked very good in choreography that wasn’t easy. Associate artistic director Sheldon B. Smith also revealed glimpses of a new piece, Dog-Leg Drag-Line (Drum Groove Tolerance), that seemed characteristically rough, mysterious, and offhandedly humorous; he said it was about intimidation, sort of. These two premieres plus Bartoszek’s 1994 Clearing, Made of Dream and 1986 Flight/Fight Dance make up the program for the first weekend of four celebrating Hedwig’s tenth anniversary, next Thursday-Saturday, May 4-6, at 8 in the dance studio of the Chicago Cultural Center, 78 E. Washington; $8-$12. The program May 11-13 and 18-20 includes these two new works plus a third, a collaboration between Bartoszek and Bharatanatyam dancer Hema Rajagopalan, as well as Bartoszek’s 1989 I Depend on Tango and Smith’s 1994 Duet for Two III. The final weekend, May 25 and 26, is a Hedwig Dance Lab reunion concert, with new works by Alt, Ann Boyd, Marianne Kim, Julia Mayer, and Rebecca Rossen. Call 907-2192 for tickets and info.