Brief background & history of the alto flute
The alto flute is a lower and somewhat more unusual member of the flute family than the piccolo and concert C flute. Sounding a perfect fourth lower than the flute in C, it has a sounding range from G below middle C to the G three octaves higher. Its sound differs from that of the C flute, despite its similar compass, due to the fundamental differences in size necessary to enable to lowest pitches to sound. The internal diameter (bore size) of the alto may be up to seven millimetres larger than that of the C flute, and is considerably longer, measuring approximately 880mm, compared to the 685mm of the C flute. The basic design of a standard alto flute is the same as the C flute, with the specifications proportionally larger and extra levers attached to some of the keys to allow for the large space between tone holes.
The exact origin of the alto flute is unknown, although large flutes have been in existence for several hundred years. Early flutes were tuned to different pitches, to cover a wider range of pitches than was possible with the limited compass of instruments without keys. Early use of flutes was predominantly military. Flutes were later used to add an instrumental colouring to vocal lines, and eventually became exponents of instrumental music in the form of a consort of similar sounding instruments with different pitch ranges. There are thought to have been soprano, alto, tenor and bass flutes, tuned a perfect fifth apart with a pitch range limited to approximately an octave. The modern C flute, with a much greater extension of range than the earlier instruments, is an amalgamation of the alto and tenor versions of these early flutes. The bass member of the family, pitched in G, suffered from a number of impracticalities due to its necessary size, and became virtually obsolete until Boehm's work to modernise it in the mid 19th century.
There were numerous problems with the early alto flute. In addition to suffering from the problems associated with all simple-system flutes, such as complicated cross fingerings and inconsistent intonation, the length of the tube itself caused compounded difficulties for the performer. Finger holes were widely spaced, due to their necessary positioning for tuning purposes, and were large and difficult to cover with the fingers. The length of the tube meant that a player was required to employ a large stretch of the arms, particularly to reach the left hand finger holes, which were positioned further away from the body than Boehm's key mechanism now allows. Wooden flutes have a thicker wall than modern metal flutes, and coupled with the large bore size, the early alto flute was difficult to hold, with a large stretch for the left hand. The instrument was really suitable only for a large male to play, and even then with some discomfort. It is unlikely that a female would have been physically big enough to play the alto flute.
It was not until the mid 1850s that Boehm developed his alto flute in G. The exact date of its invention is unknown, though there is documentary evidence to suggest that he made his first alto flute in 1854 or 1855, when he was 60 years old. The first alto flute in the workshop ledger appears in January 1858, and was sold to Marcel Ciemirski in Lemburg for 156 florins. There are references in letters of 1865 which suggest that the alto flute was already well established.
In creating the new instrument, Boehm set out to solve many of the problems of earlier low pitched flutes, by subjecting it to the logical key systems already used in his 1832 and 1847 designs for C flutes, which by this time were becoming more widely used. In adapting the alto flute to the now commonly termed 'Boehm System', he enabled players of his C flute to switch to the alto whenever necessary, without having to learn a new system of fingerings. He also added levers to reduce the previously limiting finger stretches, which had been necessary due to the distance between finger holes.
Perhaps the most important factor to consider was Boehm's ideal in creating this instrument. Low flutes had previously been used to form part of a consort of identical sounding instruments at different pitches. Boehm saw the role and potential of the alto flute as being more than this, adapting the instrument to enable it to become a new instrument in its own right, similar to but at the same time independent from the flute in C:
'The long felt need for deeper, stronger, and at the same time more sonorous flute tones has not been satisfactorily provided for either by the former "flute d'amour" or by the extension to the foot of a C flute, since the tones thus obtained are weak and uncertain, and their combination difficult and entirely impracticable. There must be created an entirely new instrument in the family of flutes of deeper pitch, similar to the basset-horn and the English horn.'
Boehm did more than add keys to an existing instrument. To realise his vision of an instrument with a completely new quality of sound, he created an alto flute that was in exact proportion with the C flute. He retained the necessary length of tube, but proportionally increased the bore size to support the low register. Surviving examples of his alto flutes have a bore size of 26mm, seven millimetres larger than that of the C flute. The positioning and size of the keys was calculated according to the same schema used for the manufacture of his C flutes, but based on the larger dimensions of the alto flute. In this way, he created an instrument ideally suited to its lowest register, which also had a unique tone quality in the pitches it had in common with the flute in C.
The alto flute was first constructed in England in 1891 by Rudall Carte & Co in London. At the time, the alto was the lowest member of the flute family, and was sold under the name of 'Bass Flute in G'. The later invention of a still lower member of the flute family, pitched in C to sound one octave below the concert flute, caused considerable confusion amongst players. In modern times, composers have adopted the terms 'Alto Flute in G' and 'Bass Flute in C'. However, older works using the alto flute sometimes refer to the instrument as the Bass Flute in G. This may be seen in various orchestral scores, including the Planets Suite by Gustav Holst.
The modern standard alto flute has changed little since Boehm's time. The key connection rods are now placed along the same side of the flute's body, and instruments are available in a number of different materials, most commonly nickel silver and silver. However, different makers have different key configurations and use different bore sizes. so there is considerable variation in tone quality, response and hand positions between makes.
The Kingma System alto flute was developed by Dutch flutemaker Eva Kingma in the early 1990s. The flute uses a standard open-holed key system, with a C sharp trill key and six extra keys. These extra keys allow small keys to be placed over open holes on the keys that cannot be operated directly by the fingers (for example in the G sharp key and thumb keys), to allow for even quartertones across the range of the instrument.