Question:  Sigur Rós' EP consists of the songs the group composed for an American dancer and choreographer who was at the forefront of the American modern dance for more than how many years?
Sentence (from "Merce Cunningham"): Mercier Philip "Merce" Cunningham (April 16, 1919 – July 26, 2009) was an American dancer and choreographer who was at the forefront of the American modern dance for more than 50 years.
Relevant evidence: Yes