Boehm system

The Boehm system is a system of keywork for the flute, created by inventor and flautist Theobald Boehm between 1831 and 1847.

Prior to the development of the Boehm system, flutes were most commonly made of wood, with an inverse conical bore, eight keys, and tone holes (the openings where the fingers are placed to produce specific notes) that were small in size, and thus easily covered by the fingertips. Boehm's work was inspired by an 1831 concert in London given by soloist Charles Nicholson who, with his father in the 1820s, had introduced a flute constructed with larger tone holes than were used in previous designs. This large-holed instrument could produce greater volume of sound than other flutes, and Boehm set out to produce his own large-holed design.

In addition to large holes, Boehm provided his flute with "full venting", meaning that all keys were normally open (previously, several keys were normally closed, and opened only when the key was operated). Boehm also wanted to locate tone holes at acoustically optimum points on the body of the instrument, rather than locations conveniently covered by the player's fingers. To achieve these goals, Boehm adapted a system of axle-mounted keys with a series of "open rings" (called brille, German for "eyeglasses", as they resembled the type of eyeglass frames common during the 19th century) that were fitted around other tone holes, such that the closure of one tone hole by a finger would also close a key placed over a second hole.

In 1832 Boehm introduced a new conical-bore flute, which achieved a fair degree of success. Boehm, however, continued to look for ways to improve the instrument. Finding that an increased volume of air produced a stronger and clearer tone, he replaced the conical bore with a cylindrical bore, finding that a parabolic contraction of the bore near the embouchure hole improved the instrument's low register. He also found that optimum tone was produced when the tone holes were too large to be covered by the fingertips, and he developed a system of finger plates to cover the holes. These new flutes were at first made of silver, although Boehm later produced wooden versions.

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