The contralto voice in opera and classical music has a range which typically lies between the F below middle C (F3) to two Fs above middle C (F5). In the lower and upper extremes, some contralto voices can sing from the E below middle C (E3) to two B♭s above middle C (B♭5). The contralto voice has the lowest tessitura of the female voices and is noted for its rich and deep vocal timbre. True operatic contraltos are very rare. The following is a list of contralto singers who have regularly performed unamplified classical or operatic music in concert halls and/or opera houses.