they used to be called the money notes. - you had to sing those high c's — and if you didn't, the whole - performance was ruined. juan diego's status as one of the world's leading tenors has earned him great admiration. and he comes to the stage at the royal opera house to give masterclasses to aspiring opera stars. this high note is here, yeah? it's not here, it's not here. but it's not here either, it's in the middle. when you give a masterclass and hear different singers, you already know, when you have listened to them, who might become a superstar 01’ an opera singer. and you already know who won't.