Mr. Cunningham ranks with Isadora Duncan, Serge Diaghilev, Martha Graham and George Balanchine in making people rethink the essence of dance and choreography, posing a series of “But” and “What if?” questions over a career of nearly seven decades.



He went on doing so almost to the last. Until 1989, when he reached the age of 70, he appeared in every single performance given by his company, Merce Cunningham Dance Company; in 1999, at 80, though frail and holding onto a barre, he danced a duet with Mikhail Baryshnikov at the New York State Theater. And in 2009, even after observing his 90th birthday with the world premiere of the 90-minute “Nearly Ninety,” at the Brooklyn Academy of Music he went on choreographing for his dancers, telling people as they went to say farewell to him that he was still creating dances in his head.