In real life as well as on the theatrical stage, the voice is just one out of the many external features of a person such as facial expression, gestures and general appearance which inform us about his inner character. In opera, because of its very nature, the singing voice assumes a more dominant role. In analogy to the visual mask of old (the persona in the original meaning of the word), which conveyed to the theatre audience the character of the dramatic role, the voice type allocated to an operatic part can be regarded as an auditory mask, which through its distinctive tone quality provides an impersonation of the operatic character. In the same way as the visual mask was intended to give a broad idea of the kind of character appearing on the dramatic stage, the auditory mask of the voice type is meant to be expressive of the character type represented by the operatic personage.