Alto flute

The alto flute is an instrument in the Western concert flute family, the second-highest member below the standard C flute after the uncommon flûte d'amour. It is the third most common member of its family after the standard C flute and the piccolo. It is characterized by its rich, mellow tone in the lower portion of its range. It uses the same fingerings as the C flute and piccolo, but is a transposing instrument in G (sounding a perfect fourth lower than written).

The bore of the alto flute is considerably larger in diameter and longer than a C flute and requires more breath from the player. This gives it a greater dynamic presence in the bottom octave and a half of its range.

It was the favourite flute variety of Theobald Boehm, who perfected its design.

Its range is from G₃ (the G below middle C) to G₆ (4 ledger lines above the treble clef staff) plus an altissimo register stretching to D♭₇. The headjoint may be straight or curved.

British music that uses this instrument often refers to it as a bass flute, which can be confusing since there is a distinct instrument known by that name. This naming confusion originated in the fact that the modern flute in C is pitched in the same range as the Renaissance tenor flute; therefore, a lower pitched instrument would be called a bass.