Local ballet lovers often feel starved for ballets by the incomparable George Balanchine, especially performances set to live music. They and everyone else will get both when the St. Paul Chamber Orchestra joins the feisty Pittsburgh Ballet Theatre for a concert of three works to music by Mozart. Balanchine’s “Divertimento No. 15,” a heady combo of neoclassical idealism and sensual gaiety, is the kind of sublime ballet that critics call “celestial” and “majestic.” By contrast, two ballets by Czech choreographer Jirí Kylián present quite a different worldview. Kylián has said, “Our bodies are 275 hinges or joints, so the combination of what you can do with them is endless.” His “Petite Mort” integrates athletic men wielding fencing foils, women defiantly stepping out of baroque dresses, and elegant mating dances. His lively “Sechs Tänze,” set to Mozart’s “Six German Dances,” allies the sophisticated with the absurd, pompous powdered wigs with sly wit. Operatic intensity abounds.