tessitura
The range of pitches in which a vocal or instrumental part lies most consistently, as distinct from its absolute range.
In Depth
Tessitura (Italian for "texture") refers not to the highest or lowest notes a voice or instrument can reach, but to the pitch zone where the music sits most of the time. A soprano role might have an absolute range from middle C to high C, but if most of the music sits between G4 and A5, that is its tessitura. A singer might be capable of reaching extreme high notes but find a role exhausting if its tessitura sits too consistently in the upper part of their range.
Tessitura is often more important than range in determining whether a role or piece suits a particular voice. A dramatic soprano and a lyric soprano might have similar absolute ranges, but the dramatic soprano's voice is built for a higher, more demanding tessitura. Opera casting directors consider tessitura carefully: a role with a few high notes is less taxing than one that sits high throughout. The concept also applies to instruments — a clarinet part with a high tessitura will have a brighter, more penetrating character than one that sits in the instrument's low register.
Verdi was notorious for writing roles with punishingly high tessituras — his Otello sits so consistently in the tenor's upper range that performing it is considered one of the most physically demanding feats in opera.