Yeah Nussum Dorma is the theme aria in Turandot sung by the tenor. The theme for the princess (the heroine) is actually from a song I learned when I was a kid - it is the Sui sen hua (water angel flower - a Chinese folk song). It is a typical Chinese folk song and Puccini ( I think he visited China) had picked that tune and turned it into the theme of Turandot. I like that opera very much and I have seen it at least 4 times if not more.