Tessitura (from the Italian tessitura — “texture,” “fabric”) is a term denoting the part of the pitch range of a voice or instrument in which the overwhelming majority of a particular work's notes lie. It should not be confused with range: range is all the possible notes from lowest to highest, whereas tessitura is where the voice “lives” most of the time.
Tessitura may be high, medium, or low. A work with a high tessitura demands that the singer remain for long stretches in the upper register, which is physically difficult even if the individual highest notes are within reach. That is why tessitura is an important practical criterion in choosing repertoire and classifying voices (soprano, tenor, bass, and so on). A comfortable tessitura allows a performer to sing freely and expressively without tiring the voice.
