There was a craze about sleepwalking in the thirties of the nineteenth century. In the midst of this, Bellini wrote this opera, with its notoriously difficult lead role. In the sixties it was one Dame Sutherland’s big successes on stage in London and New York, following in the footsteps of Maria Callas in the fifties.
Amina is betrothed to Elvino, but he is a bit of a jealous type. So when she was found in the room of another man, Elvino quickly decided she was not faithful to him, and broke off the engagement. People were telling him it wasn’t true, that she was innocent, but to no avail. Of course the role of his former love Lisa in this was circumspect.
In the second act he is to marry Lisa instead, but then everyone is seeing the again sleepwalking Amina on a dangerous location. It finally is clear to mr überjealous that she was actually sleepwalking, like everyone was telling him: he saw her do it. The opera ends in the marriage of Amina and Alvino.
Interestingly, Cecilia Bartoli sang this role in 2008, following Maria Malibran, a famous Spanish singer. Bartoli published a very interesting album centred around Malibran, just a year before.
The difficulty of the role lies in many things: from the trills and the florid technique, to the huge range that is required. It was made for a voice that ranges from the mezzo-soprano to the higher ranged soprano. There are not many that can do all of this.