Not just any company gets to produce the vibrant works of choreographer George Balanchine, whose quick-paced, high-energy style revolutionized ballet. But City Ballet of San Diego has the technical skills and artistic brilliance required by the Balanchine Trust to mount his dances. Now, they present Balanchine Masterworks, a performance of three of the great artist's full-length masterworks at Spreckels Theatre. Feast your eyes and ears on Concerto Barocco, an homage by the great composer Bach, along with Emeralds, his dreamy, romantic tribute to the green jewel set to the music of Gabriel Faure. Finally, there's the San Diego premiere of Square Dance, a couples ballet set to the music of Stravinski and Corelli that captures the high spirits of Western square dancing.