In the picture at the left, Glen Newton holds (left to right) an E-flat soprano flute, a C flute, and an alto flute.
The C flute is the instrument commonly found in bands and orchestras. The one shown here has a "B foot", a variation of the lower joint that extends the range an extra half step to the B below middle C.
The E-flat soprano flute (usually simply called the E-flat flute, since it is the only flute pitched in E-flat) is pitched three half steps above the C flute. Its music is written transposed down three half steps. Thus a "G" played on this instrument would sound the same pitch as a "B-flat" played on the C flute. This is almost the same transposition as used for the E-flat alto saxophone; it's just an octave different. This makes it very convenient for an E-flat flute player to read alto sax music. The flute will sound an octave higher than the sax playing the same written notes.
The alto flute is pitched in G, a perfect fourth below the C flute. Its lowest note is the same as the lowest note on the violin, making it a convenient substitute for a second violin in chamber music ensembles (when the part doesn't require double stops or extreme high range). Music for the alto flute is written transposed up five half steps. The alto flute provides an important voice in jazz, flute ensembles, and some motion picture scores. It is used in some orchestral works (in which it is sometimes referred to as a "bass flute" because of the changing nomenclature during the development of the flute family). Like the C flute, the alto flute blends well with the human voice.
The diameter of each flute's body is proportional to its length, and this difference in body size gives each instrument a slightly different sound. When they play the same note, the alto flute sounds "deeper" or "mellower" and the E-flat flute sounds "thinner" or "more brilliant" in comparison with the standard C flute.