Alto
The low female or boy's voice, lying between soprano and tenor.
What it means
Alto denotes the lowest of the classical female voice types, and occasionally the corresponding boy's voice, sitting in the voice system of a mixed choir between soprano and tenor. The name derives from the Latin altus, “high,” originally referring to the highest male voice in polyphonic music, from which today's meaning developed.
The alto's range typically spans from about the F below middle C to roughly the F two octaves above, though the exact placement shifts depending on voice type and repertoire. Tonally, the alto is marked by a darker, warmer color than the soprano, with comparable agility in the middle register.
Musical use
In four-part choral writing, the alto usually takes the second-highest line and often carries a harmonically filling part that is less melodically prominent than the soprano's. In operas and oratorios, alto voices frequently cast more mature, maternal, or dark, dramatic roles.
The voice type alto should be distinguished from the use of the word for instruments of a certain range, such as the alto flute, alto trombone, or alto saxophone: here the voice-type concept is transferred to the range of an instrument within an instrument family.
Historically, the alto voice in sacred music was long reserved for men singing as falsettists or countertenors, since women were barred from participating in many liturgical contexts; only as women's voices were gradually admitted did the alto become the regular female voice known today.
Performance practice
If you sing alto in a choir or ensemble, pay particular attention to a well-supported middle register, since most of the harmony-carrying notes sit there. Support the tone well even in quieter passages, so the inner voice does not get lost in the overall sound but keeps the harmonic foundation audible.