Pyrophone

A pyrophone, also known as a "fire/explosion organ" or "fire/explosion calliope" is a musical instrument in which notes are sounded by explosions, or similar forms of rapid combustion, rapid heating, or the like, such as burners in cylindrical glass tubes, creating light and sound. It was invented by physicist and musician Georges Frédéric Eugène Kastner (born 1852 in Strasbourg, France - died 1882 in Bonn, Germany), son of composer Jean-Georges Kastner, around 1870.

It is well known that if a flame of hydrogen gas be introduced within a glass or other tube, and if it be so placed as to be capable of vibrating, there is formed around this flame—that is to say, upon the whole of its enveloping surface—an atmosphere of hydrogen gas, which, in uniting with the oxygen in the air of the tube, burns in small portions, each composed of two parts of hydrogen to one of oxygen, the combustion of this mixture of gases producing a series of slight explosions or detonations.

If such a gaseous mixture, exploding in small portions at a time, be introduced at a point about one-third of the length of the tube from the bottom, and if the number of these detonations be equal to the number of vibrations necessary to produced a sound in the tube, all the acoustic conditions requisite to produce a musical tone are fulfilled.

The pyrophone is similar to the steam calliope, but the difference is that in the calliope the combustion is external to the resonant cavity, whereas the pyrophone is an internal combustion instrument. The difference initially seems insignificant, but external combustion is what gives the calliope its staccatto. Operating under the constant pressures of an external combustion chamber, the calliope merely directs exhaust (HB# 421.22: internal fipple flutes). By controlling the combustion specific to each resonant chamber, the pyrophone has, for better or worse, a greater range of variables in play when producing tones. In a purely mechanical (non-solenoid) calliope, the resulting pressures of external combustion result in between one and five pounds of trigger pressure. In a mechanical pyrophone, trigger weight per key is related to comparatively lower backpressure of combustible gas. Again, the force of combustion happens in the resonance chamber; rather than controlling the exhaust of an explosion that has already happened in order to produce tones, the pyrophone controls the explosion to produce the tone.

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