Less frequently heard than the flute or piccolo, the alto flute has a warm mellow sound, and generally does not project as well as the flute or piccolo. When playing the alto flute, performers use all the same fingerings as the flute and will sound a perfect fourth lower. It has a comfortable playing range of “g” to “g3.” Alto flutes are usually made of silver or nickel with silver plating. The alto flute consists of three parts: the headjoint, middlejoint and footjoint. Because the alto flute is considerably larger than the flute, players can choose between a long, straight headjoint and a shorter, curved option. Instrument makers also produce alto flutes with key extensions that make the instrument easier to hold. Players blow into the mouth hole of the headjoint, covering a quarter to a third of the hole with their bottom lip and using the upper lip to blow downward. By blowing into the lip hole, the performer creates a vibrating column of air that makes a sound. The pitch of the sound is determined by keys that are depressed and thus change the length of the air column. To articulate notes, the player touches the tongue behind the upper teeth, as if saying “too.” Compared to the flute, the alto flute requires a more relaxed lip position and less air pressure.
The alto flute first appeared in Renaissance times, when flutes of various sizes were used to double soprano, alto, tenor and bass vocal lines. During the Baroque era, composers often wrote for the flute d’amour, a close relative to the alto flute. While there were many attempts to improve the alto flute in the nineteenth century, Theodore Boehm is responsible for designing the alto flute played today. After designing the silver flute around 1847, Boehm finished his alto flute design in 1855.

The alto flute is an integral part of most flute choirs, with its low warm sound adding depth to the ensemble. It sometime shares its low role with the bass flute, which is even bigger than the alto flute and sounds an octave below the standard flute. In the late nineteenth century, composers began including the alto flute in orchestral works scored for large orchestra. Important alto flute solos can be heard in Ravel’s Daphnis and Chloe and Stravinsky’s Rite of Spring. While there is limited solo repertoire for the alto flute, Toru Takemitsu’s Toward the Sea for alto flute and guitar demonstrates the beautiful tonal possibilities of the instrument.