Literally, “tessitura” is the Italian for “texture.” So it isn’t just the range of pitches that is included in the concept of “tessitura”, but also their arrangement. Examples of differences in tessitura include: does the piece have mostly sudden or gradual rises and falls in pitch; the relative number of very high or low notes, not just the total range; whether lines and phrases of music in the piece tend to rise or fall – the muscular tendencies of a singer may be more suited to one or the other direction. Speed of the changes in pitch is also a factor.
The ability to sing pieces with fast or slow note-changes is related to the muscular tendencies of a singer. This difference may be similar to, or identical to, the distinction made in sports medicine between slow-twitch and fast-twitch muscular abilities. Singers who can change pitch easily and gracefully may have difficulty singing long, sustained passages, and vice versa. Young singers need to learn this and until they do, may choose pieces which they can’t sing well — the tessitura needs to be considered.