When discussing the recent MET performances of Il Trovatore, with some os my blog followers, the name of several mezzo-sopranos was mentioned, namely the great Azucena from Fiorenza Cossotto. Another name mentioned was Shirley Verrett.
The career of Shirley Verrett is very interesting because she started as a mezzo-soprano and "moved" to soprano.
When a think in Verrett I always remember the fenomenal performance of L'Assedio di Corinto in MET in 1977 (with Beverly Sills) and the performances of Macbeth in La Scala 1975/76.
Here are two videos from those performances (for L'Assedio di Corinto follow the link).