Online Opera originated in Italy. West End musicals are the London equivalent of America's Broadway. Your article addressed well the issue of Western classical opera, but did not really cover 20th century popular musical theatre. I would be very interested to hear anything you have to say on this matter. Thank you so much for your time.
Opera is a highly stylized form of music drama in the Western tradition.
But what distinguishes it from 'musicals' as we know them is the stylized vocal manner. Opera originated in Italy. Artists require intense training in vocal technique, similar to our Indian tradition of classical vocal music. Actually, you only need hear it to tell the difference in styles. As a lighter version of opera evolved into operatta, it grew closer to what we know as music theatre.