STRAINS OF LONG SILVER TRUMPETS and the deepthroated chanting of monks greeted the arrival of His Holiness the Fourteenth Dalai Lama, Tenzin Gyatso, at the Asian Art Museum of San Francisco in April. The religious and temporal leader of Tibet's exiled Buddhist population had come to grant a special blessing, initiating the creation of a large-scale sand mandala for the opening of "Wisdom and Compassion: The Sacred Art of Tibet." This stunning exhibition of Tibetan paintings, sculpture, and tapestries dating from 900 to 1900 C.E. has been assembled from prominent museums and private collections in North America, Europe, and the Soviet Union. Notably, none of the pieces were borrowed from either institutional or official sources in the People's Republic of China, to which Tibet has been politically bound for more than thirty years.