Complex sentence: The concerto was choreographed by George Balanchine as "Balustrade" in 1941, but only premiered as a Ballet in 1972, by New York City Ballet as part of the Stravinsky Festival.
Split into simpler sentences: The concerto was choreographed by George Balanchine as "Balustrade" in 1941. It was premiered by New York City Ballet as part of the Stravinsky Festival.