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 "Philip Glass Ensemble"): After Glass wrote his first opera, "Einstein on the Beach", for the Ensemble in 1976, he began to compose for other instrumentation more frequently, but he still retains the core ensemble instrumentation.
Relevant evidence: Yes