Male singers can be classified by vocal range as bass, bass-baritone, baritone, tenor and countertenor, and female singers as contralto, mezzo-soprano and soprano.
en.wikipedia.org Her use of her contralto register was likened to dipping into a deep, mysterious well to scoop up a trove of buried riches.
en.wikipedia.org A demanding work, it requires 14 soloists (three sopranos, one contralto, two tenors, four baritones, and four basses).
en.wikipedia.org She also occasionally played some of the larger contralto roles.
en.wikipedia.org The opera is scored for one soprano, one contralto, and one tenor, two saxophones, and orchestra.
en.wikipedia.org