L. Bernstein: WEST SIDE STORY Balcony Scene Tony: Ioannis Kalyvas Maria: Myrsini Margariti National Symphony Orchestra of Greek Radio and Television - ERT Conductor: Loukas Karytinos
You are aware that Bernstein actually wanted an opera and not a musical? It is just that these singers are classically trained but it is certainly not the same as opera. Overall, classical musicals can be performed from classically trained singers.
Do yourself the favour and listen to the recording by Leonard Bernstein himself. He personally chose the singers according to his idea of the "West Side Story". At the end José Carreras was singing Tony and Kiri te Kanawa was singing Maria.