BOMBARDON, or Bass Tuba, the name given to the bass and contrabass of the brass wind in military bands, called in the orchestra bass tuba.
The name of bombardon is unquestionably derived from bombardone, the Italian for contrabass pommer (bombard), which, before the invention of the fagotto, formed the bass of medieval orchestras; it is also used for a bass reed stop of 16 ft. tone on the organ. The bombardon was the very first bass wind instrument fitted with valves, and it was at first known as the corno basso, clavicor or bass horn (not to be confounded with the bass horn with keys, which on being perfected became the ophicleide). The name was attached more to the position of the wind instruments as bass than to the individual instrument. The original corno basso was a brass instrument of narrow bore with the pistons set horizontally. The valve-ophicleide in F of German make had a wider bore and three vertical pistons, but it was only a "half instrument," measuring about 12 ft. A. Kalkbrenner, in his life of W. Wieprecht (1882), states that in the Jäger military bands of Prussia the corno basso (keyed bass horn) was introduced as bass in 1829, and the bombardon (or valve-ophicleide) in 1831; in the Guards these instruments were superseded in 1835 by the bass tuba invented by Wieprecht and J.G. Moritz.
The modern bombardon is made in two forms: the upright model, used in stationary band music; and the circular model, known as the helicon, worn round the body with the large bell resting on the left shoulder, after the style of the Roman cornu (see Horn), which is a more convenient way of carrying this heavy instrument when marching. The bombardon, and the euphonium, of which it is the bass, are the outcome of the application of valves to the bugle family whereby the saxhorns were also produced. The radical difference between the saxhorns and the tubas (including the bombardon) is that the latter have a sufficiently wide conical bore to allow of the production of fundamental sounds in a rich, full quality of immense power. This difference, first recognized in Germany and Austria, has given rise in those countries to the classification of the brass wind as "half" and "whole" instruments (Halbe and Ganze Instrumente). When the brass wind instruments with conical bore and cup-shaped mouthpiece first came into use, it was a well-understood principle that the tube of each instrument must theoretically be made twice as long as an organ pipe giving the same note; for example, the French horn sounding the 8 ft. C of an 8 ft. organ pipe, must have a tube 16 ft. long; C then becomes the second harmonic of the series for the 16 ft. tube, the first or fundamental being unobtainable. After the introduction of pistons, instrument-makers experimenting with the bugle, which has a conical bore of very wide diameter in proportion to the length, found that baritone and bass instruments constructed on the same principle gave out the fundamental full and clear. A new era in the construction of brass wind instruments was thus inaugurated, and now that the proportions of the bugle have been adopted, the tubes of the tubas are made just half the length of those of the older instruments, corresponding to the length of the organ pipe of the same pitch, so that a euphonium sounding 8 ft. C no longer needs to be 16 ft. long but only 8 ft. The older instruments, such as the saxhorns, with narrow bore, have therefore been denominated "half instruments," because only half the length of the instrument is of practical utility, while the tubas with wide bore are styled "whole instruments."  Bombardons are made in E flat and F of the 16 ft. octave, corresponding to the orchestral bass tuba, double bass in strings, and pedal clarinet and contrafagotto in the wood wind. The bombardon in B flat or C, an octave lower than the euphonium, corresponds to the contrabass tuba in the orchestra.
The bombardons possess a chromatic compass of 3 to 4 octaves. The harmonic series consists of the harmonics from the 1st to the 8th.
Bombardon in E Flat.
Harmonic Series of the Contrabass Bombardon in C.*
The lowest notes produced by the valves are very difficult to obtain, for the lips seldom have sufficient power to set in vibration a column of air of such immense length, at a rate of vibration slow enough to synchronize with that of notes of such deep pitch.  Even when they are played, the lowest valve notes can hardly be heard unless doubled an octave higher by another bombardon.
Bombardons are generally treated as non-transposing instruments, the music being written as sounded, except in France and Belgium, where transposition is usual. The intervening notes are obtained by means of pistons or valves, which, on being depressed, either admit the wind into additional lengths of tubing to lower the pitch, or cut off a length in order to raise it. Bombardons usually have three or four pistons lowering the pitch of the instrument respectively 1, , 1 and 2 tones (in Belgium, 1, , 2 and 3 tones). The valve system, disposal of the tubing and shape and position of the bell differ considerably in the various models of well-known makers. In Germany and Austria  what is known as the cylinder action is largely used; for the piston or pump is substituted a four-way brass cock operated by means of a key and a series of cranks.
In order to obtain a complete chromatic scale throughout the compass, there must be, as on the slide-trombone, seven different positions or lengths of tubing available, each having its harmonic series. These different lengths are obtained on the bombardon by means of a combination of pistons: the simultaneous use of Nos. 2 and 3 lowers the pitch two tones; of Nos. 1, 2 and 3, three tones; of Nos. 1, 2, 3, 4, five and a half tones, etc. A combination of pistons, however, fails to give the interval with an absolutely correct intonation, since the length of tubing thrown open is not of the theoretical length required to produce it. Many ingenious contrivances have been invented from time to time to remedy this inherent defect of the valve system, such as the six-valve independent system of Adolphe Sax; the Besson Registre, giving eight independent positions; the Besson compensating system Transpositeur; the Boosey automatic compensating piston invented by D.J. Blaikley, and V. Mahillon's automatic regulating pistons. More recently the Besson enharmonic valve system, with six independent tuning slides and three pistons, and Rudall, Carte & Company's new (Klussmann's patent) bore, conical throughout the open tube and additional lengths, have produced instruments which leave nothing to be desired as to intonation. (See Valves and Tuba.)
 See Dr E. Schafhäutl's article on Musical Instruments, section 4 of Bericht der Beurtheilungscommission bei der Allg. deutschen Industrie-Ausstellung, 1854 (Munich, 1855), pp. 169-170; also Friedr. Zamminer, Die Musik und die Musikinstrumente in ihrer Beziehung zu den Gesetzen der Akustik (Giessen, 1855), p. 313.
 V.C. Mahillon, Eléments d'acoustique musicale et instrumentale (Bruxelles, 1874), p. 153.
 The bombardon is used in the military bands of Austria, but in those of Germany it has been superseded by a bass tuba differing slightly in form and construction from the bombardons and bass tubas used in England, France, Belgium and Austria.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)