Bugle, Bugle-horn, Keyed Bugle, Kent Bugle or Regent's Bugle (Fr. Bugle, Clairon, Cor à clefs, Bugle à clefs; Ger. Flügelhorn, Signalhorn, Bugelhorn, Klappenhorn, Kenthorn; Ital. Corna cromatica), a treble brass wind instrument with cup-shaped mouthpiece and conical bore, used as a military duty and signal instrument. The bugle was originally, as its name denotes, a bull's horn,[1] of which it has preserved the characteristic conical bore of rapidly increasing diameter.

Those members of the brass wind such as the horns, bugle, trumpet and tubas, which, in their simplest form, consist of tubes without lateral openings, depend for their scale on the harmonic series obtained by overblowing, i.e. by greater pressure of breath and by the increased tension of the lips, acting as reeds, across the mouthpiece. The harmonic series thus produced, which depends on the acoustic principles of the tube itself, and is absolutely uninfluenced by the manner in which the tube is bent, forms a natural subdivision in classifying these instruments: - (1) Those in which the lower harmonics from the second to the sixth or eighth are employed, such as the bugle, post-horn, the cornet à pistons, the trombone. (2) Those in which the higher harmonics from the third or fourth to the twelfth or sixteenth are mostly used, such as the French horn and trumpet. (3) Those which give out the fundamental tone and harmonics up to the eighth, such as the tubas and ophicleide.

Harmonic Series.

We thus find a fundamental difference between the trumpet and the bugle as regards the harmonic series. But although, to the casual beholder, these instruments may present a general similarity, there are other important structural distinctions. The tube of the trumpet is cylindrical, widening only at the bell, whereas that of the bugle, as stated above, is conical. Both instruments have cup-shaped mouthpieces outwardly similar. The peculiar shape of the basins, however, at the place where they open into the tube, angular in the trumpet and bevelled in the bugle, taken in conjunction with the bore of the main tube, gives to the trumpet its brilliant blaring tone, and to the bugle its more veiled but penetrating quality, characteristic of the whole family.[2] Only five notes are required for the various bugle-calls, although the actual compass of the instrument consists of eight, of which the first or fundamental, however, being of poor quality, is never used. There are bugles in C and in E flat, but the bugle in B flat is most generally used; the key of C is used in notation.

In order to increase the compass and musical possibilities of the bugle, two methods have been adopted, the use of (1) keys and (2) valves. The application of keys to the bugle produced the Kent bugle, and later the ophicleide. The application of valves produced the family of saxhorns. The use of keys for wood wind instruments was known early in the 15th century,[3] perhaps before. In 1438, the duke of Burgundy paid Hennequin Haulx, instrument-maker of Brussels, 4 ridres a piece for three tenor bombards with keys. In the 16th century we find a key applied to the bass flûte-à-bec[4] and later to the large tenor cornetto.[5] In 1770 a horn-player named Kölbel, belonging to the imperial Russian band, experimented with keys on the trumpet, and in 1795 Weidinger of Vienna produced a trumpet with five keys. In 1810 Joseph Halliday, the bandmaster of the Cavan militia, patented the keyed bugle, with five keys and a compass of twenty-five notes, calling it the "Royal Kent Bugle" out of compliment to the duke of Kent, who was at the time commander-in-chief, and encouraged the introduction of the instrument into the regimental bands.

A Royal Kent bugle in C, stamped with Halliday's name as inventor, and made by P. Turton, 5 Wormwood Gate, Dublin, was exhibited by Col. Shaw-Hellier at the Royal Military Exhibition in 1890.[6] The instrument measures 17 in., and the total length of the tubing, including the mouthpiece, 50½ in. The diameter at the mouthpiece is ½ in. and at the bell 5¾ in. The instrument has a chromatic compass of two octaves, Chromatic compass. the open notes being Open notes. .

Mahillon (op. cit. p. 117) points out that the tonality of the key-bugle and kindred instruments is determined by the second harmonic given out by the open tube, the first key remaining open. To the original instrument specified in the patent, Halliday added a sixth key, which became the first and was in the normal position open; this key when closed gave B flat, with the same series of harmonics as the open tube. The series, however, becomes shorter with each successive key. Thus, on being opened, the second key gives Second key. , the third key Third key. , the fourth key Fourth key. , the fifth key Fifth key. , the sixth key Sixth key. . The bore of the instrument is just wide enough in proportion to its length to make possible the playing of the fundamental tones in the first two series, but these notes are never used, and the harmonics above the sixth are also avoided, being of doubtful intonation. In the ophicleide, the bass of the key-bugle, the bore is sufficiently wide to produce the fundamentals of a satisfactory quality.

The keyed bugle was chiefly used in B flat, a crook for B flat being frequently added to the bugle in C; the soprano bugle in E flat was also much used in military bands.

The origin of the bugle, in common with that of the hunting horn, is of the highest antiquity. During the middle ages, the word "bugle" was applied to the ox and also to its horns, whether used as musical instruments or for drinking. The New English Dictionary quotes a definition of bugle dating from c. 1398: "The Bugle ... is lyke to an oxe and is a fyers beest."[7] In 1300 a romance[8] contains the word used in both acceptations, "A thousand bugles of Ynde," and "tweye bugle-hornes and a bowe." F. Godefroy[9] gives quotations from early French which show that, as in England, the word bugle was frequently used as an adjective, and as a verb: - "IIII cors buglieres fist soner de randon" (Quatre fils Aymon, ed. P. Tarbé, p. 32), and "I grant cor buglerenc fit en sa tor soner" (Aiol, 7457, Société des anciens textes français). Tubas, horns, cornets and bugles have as common archetype the horn of ram, bull or other animal, whose form was copied and modified in bronze, wood, brass, ivory, silver, etc. Of all these instruments, the bugle has in the highest degree retained the acoustic properties and the characteristic scale of the prototype, and is still put to the original use for giving military signals.