With its pastoral setting and story, "La sonnambula" was an immediate success and is still regularly performed. The title role of Amina (the sleepwalker) with its high tessitura is renowned for its difficulty, requiring a complete command of trills and florid technique, but it fitted Pasta's vocal capabilities, her soprano also having been described as a "soprano sfogato", one which designates a contralto who is capable—by sheer industry or natural talent—of extending her upper range and being able to encompass the coloratura soprano tessitura.