I discussed this a bit on my facebook the other day, but just wanted to clarify with you guys. For no big reason, just to get things straight in my mind. For fun.
A musical will have songs that help tell a greater story, as well as acting.
An opera is all songs, no acting.
A (genre) opera is all (genre) songs, where genre can be rock, punk, whatever. A (genre) musical is the same, but with acting bits.
If a cd is all songs that tell a greater story, it can be considered a (genre) opera, and also be considered a form of concept album.
Is that all there is to it? Am I missing anything? Do I understand things correctly? Is a rock opera only a rock opera if it's performed on stage or in a movie, or can it still be classified as a rock opera even if it only exists in sound form (record, cd, whatever).