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

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

In addition to large holes, Boehm provided his flute with "full venting", by which is meant that keys which previously had been normally closed (opening only when the key was operated) were converted to normally open keys. Another premise behind the Boehm system was that the tone holes should be located at acoustically optimum points on the body of the instrument, rather than where they can conveniently be 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 nineteenth century) that were fit 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 his 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. To improve the low register, he found that a parabolic contraction of the bore at the mouth hole was needed. For optimum tone he found that the tone holes should be large enough that they cannot be covered by the fingertips, and so a system of finger plates became necessary. These new flutes were at first made of silver, although Boehm later produced wooden versions.

The cylindrical Boehm flute was introduced in 1847, with the instrument gradually displacing virtually all other flutes during the second half of the nineteenth century. While non-Boehm flutes are still made in limited numbers, they are primarily restricted to non-ensemble situations such as folk music, where tuning and regularity of tone are not considered as critical.

A key system inspired by Boehm's for the clarinet family also is known as "Boehm system", although it was not developed by Boehm himself. Boehm did work on a system for the bassoon, and Boehm-inspired oboes have been made, but non-Boehm systems remain predominant for these instruments.

• Baines, Anthony (1991). Woodwind Instruments and Their History. Dover, 320-323; 326-328; 336.  (republication of third edition, 1967, as reprinted with corrections, 1977)

• Karl Ventzke, Boehm-System Bassoons in the 19th Century