Question: The Philip Glass Ensemble is a musical group founded by composer Philip Glass in 1968, his first opera is which opera in four acts (framed and connected by five "knee plays" or intermezzos), composed by Philip Glass, and directed by theatrical producer Robert Wilson?
Sentence (from "Einstein on the Beach"): It is Glass's first and longest opera score, taking approximately five hours in full performance without intermission; given the length, the audience is permitted to enter and leave as desired.
Relevant evidence: No