QcCowboy

the amount of spoken dialogue in Porgy and Bess is so minimal as to have no sway what so ever on the definition one would apply to it - opera or musical or operetta.

As a matter of fact, the spoken dialogue in Porgy is there for a very specific effect: only the black people sing. The white people speak. It's what differentiates the two very different worlds.

I can't say off-hand since I don't have a scor handy, but there may be no more than a dozen spoken lines in Porgy.

What divides an opera from an operetta is considerably more than the inclusion/exclusion of dialogue. The depth/topic of the story, and the over-all structure of the work are far greater issues in defining between the two.

As for Magic Flute being a "singspiel", I happen to believe that THAT was considerably more a question of marketing than a reference to any actual form. Magic Flute is as complex and demanding as any "opera". In essence, it IS an opera. Mozart's "modesty" is more liable to be the instigator of the "singspiel" label.

I tend to think of Sondheim's "musicals" as a sort of hybrid form. The music is highly complex, and generally heavily cyclical. The vocal lines are quite demanding. Even when his works are divided into "numbers", there's a certain ambiguity as to where exactly the number starts and finishes. Surely more the hallmark of an opera than of a musical.

Very few musicals are cyclical in their treatment of thematic material. Generally, it would be safe to presume the same for operettas.

We DO come into more complicated territory when trying to apply the opposite definitions we've just applied to musicals as pertains to opera. Not ALL operas are cyclical. Some even eschew completely any thematic links between sections of the work. Some operas have extremely frivolous and superficial subject matter.

So, see? it's all still pretty vague.