Opera singers train for many years to develop the demanding technique of unamplified singing. They also have to act as well as sing with great emotional and musical intensity. Over time, most singers learn a number of roles which they have at their command, almost at a moment’s notice which is why they can sometimes step in when a colleague falls ill. One of the most frequent causes of singers having to cancel is the common cold – if you have no voice, or cannot breathe properly it is just physically impossible to produce the required sound.

An aside: occasionally it is not the voice that is the problem. In 2009 Joyce DiDonatto broke her leg during the premier of The Barber of Seville at the Royal Opera House in central London. She thought she had just twisted her ankle when she slipped on stage and gamely carried on only to discover at A & E after the performance that she had actually fractured her right fibula. Undaunted she performed the next 4 performances in a wheel chair!

There are seven different voice types:

The highest female voice, often associated with heroines such Mimi in La bohème.
Some famous sopranos: Maria Callas, Anna Netrebko, Joan Sutherland.

Mezzo Soprano
The middle female voice which is darker and creamier than the soprano. Carmen is probably one of the most well know mezzo roles. Mezzos often play trouser roles such as Cherubino in The Marriage of Figaro. Famous mezzos include Cecilia Bartoli, Teresa Berganza, Joyce DiDonato

The lowest female voice – a deep, dark rich sound. Mistress Quickly in Verdi’s Falstaff is a good example. Kathleen Ferrier remains one of the most famous.

The highest male voice, very popular in the Renaissance and Baroque. It then almost disappeared until its rediscovery in the 20th century with Benjamin Britten writing famous roles (e.g. Oberon in A Midsummer Night’s Dream) for this voice type. Famous Countertenors include James Bowman, Alfred Deller, Andreas Scholl.

A high male voice most often associated with the hero such as Rodolfo in La bohème or Alfredo in La traviata. Famous tenors include Enrico Caruso, Placido Domingo, Jonas Kaufmann.

The middle male voice. Baritones often sing the villain – Scarpia in Tosca, or the friend to the lead male character – Rodrigo in Don Carlos. Famous baritones include Thomas Allen, Tito Gobbi, Mariusz Kwiecień.

Bass (including the slightly higher bass-baritone)
The deepest male voice . Often associated with villains such as Claggart in Britten’s Billy Budd, or comic roles such as Baron Och’s in Richard Strauss’ Der Rosenkavalier. Bryn Terfel and Willard White are bass-baritones; Boris Christoff and John Tomlinson are basses.