These are great days for Mark Morris, whose life appears charmed with possibilities. "I always can have whatever I want," said Morris, one of the dance world's most important, and most musical, choreographers, in a recent phone conversation from his apartment in the Kips Bay section of Manhattan. He meant that he enjoys complete freedom to do his work with wide parameters for his creative activity. He believes that live music goes hand-in-hand with dance performances, and he insists on it — everywhere his Mark Morris Dance Group performs, "since 1996, when it became our creed," he said.