Siegfried and Idomeneo are both what type of performances?
Idomeneo: Idomeneo, re di Creta ossia Ilia e Idamante (Italian for "Idomeneus, King of Crete, or, Ilia and Idamante"; usually referred to simply as Idomeneo, K. 366) is an Italian language opera seria by Wolfgang Amadeus Mozart.
i don't know