The Guardian: http://www.guardian.co.uk/music/2002/feb/09/classicalmusicandopera.artsfeatures
Even after reading both these articles, I still couldn't tell you, really... maybe to say operas are music driven and musicals rely on the text, but that's not altogether accurate either.
Your father picked up The Teaching Company's How to Listen to and Understand Opera with Professor Robert Greenberg, San Francisco Conservatory of Music. He's the same guy from our classical music lectures we listened to years ago with The Big Four. Sarah Grace and I will be watching these lectures with the Young Guns during the week, and the course will be in the den if you older gents are interested.
Sarah recommends the book she's reading called Opera 101. Daddy picked up several other books on opera along with four operas on DVD. Let me know if you want to watch any of them with us and we'll plan on watching them around your work schedule. He's on the waiting list for HMS Pinafore, by the way.
Also, James and Spencer are at the new Les Mis right now. I can't wait to hear what they think about the les miserables singer debate, especially after seeing it live at the Koger Center.