The term tessitura, from the Italian for 'texture', may be applied either to a piece of music or to an individual's voice.
When referring to a song, tessitura is the general (or average) position of the vocal lines. This is distinct from the range of the song, i.e., the difference between the highest and lowest notes. So, for example, a song may have a high range and a low tessitura, and vice versa. Tessitura addresses not just the range of pitches but also takes into account the arrangement of those pitches in the music, or melody, e.g., whether vocal lines and phrases in the piece tend to rise gradually or fall quickly, or whether there are large intervals between pitches, as well as the speed of pitch changes.
When applied to the singing voice, tessitura describes the most musically acceptable and comfortable timbre for a given voice type. Put simply, tessitura refers to the range of pitches in which a singer is most comfortable singing, as well as the section of a singer's range where the voice has the most pleasant-sound or tonal quality and easy volume. While a soprano and a mezzo-soprano may have a similar range (as defined by the spectrum of notes that they are both capable of singing), their tessituras will lie in different parts of that range .