She began her career as a soprano when she was only 13, but later retrained her voice as a mezzo-soprano.
en.wikipedia.org Besides the protagonist, represented by a dummy, there are 23 roles requiring seven singers (mezzo-soprano, countertenor, bass, 2 tenors, 2 baritones) and 4 dancers.
en.wikipedia.org It tells a story through 13 words: bird, despondent, cake, dog, busy, convertible, goat, hat, haberdashery, scarlet, baby, panache, and mezzo-soprano.
en.wikipedia.org A true operatic contralto is extremely rare, so much so that often roles intended for contraltos are performed by mezzo-sopranos.
en.wikipedia.org Vocally, she is best described as a soprano, though later in her career her tessitura descended to that of a mezzo-soprano.
en.wikipedia.org