Well, the thing about opera is that it is incredibly diverse. It's a musical drama arranged according to theatrical conventions (thus acts and so on) in which the parts are continually sung by classically trained singers and accompanied by an orchestra. An opera by Wagner does not sound much like a Mozart opera, a Britten opera does not sound much like one by Verdi, and an opera by Mussorgsky has remarkably little in common with one by Rossini.
Why does no one on the forum aside from a few seem to understand that this is also VERY true of emo?