Female singers (5)
(Other definitions for altos that I've seen before include "Singers" , "Highest male, lowest female, voices" , "Choir members" , "Lowest female singing voices" , "Females who sing in the lowest range" .)
(Other definitions for sopranos that I've seen before include "Females with highest singing voices" , "Female singers (opera)" , "Highest female voices" , "Female singing voices or TV mafia family" .)