Which singer possesses a four-octave vocal range?

Christina María Aguilera is an American singer, songwriter, actress and television personality. Her accolades include five Grammy Awards, one Latin Grammy Award, and a star on the Hollywood Walk of Fame. Aguilera ranked at number 58 on "Rolling Stone's" list of 100 Greatest Singers of All Time in 2008, and was included on "Time's" annual list of the 100 most influential people in the world in 2013.

Aguilera is a soprano, possessing a four-octave vocal range spanning from C3 to C♯7. Since the start of her career Aguilera's voice has been compared to that of Mariah Carey and Whitney Houston. David Browne writing for "The New York Times" noted that Aguilera's vocal performance was highly influenced by Carey and Houston, sharing that "Aguilera has been one of the foremost practitioners of the overpowering, Category 5 vocal style known as melisma", and "Ms. Carey, Ms. Houston and Ms. Aguilera, to name its three main champions, are most associated with the period from the late '80s through the late '90s".

Aguilera has, however, been criticized for her excessive use of melisma and oversinging on songs and in concerts. John Eskow of "The Huffington Post" named Aguilera a main proponent for "oversouling", described as the "gratuitous and confected melisma".