Simple short signal horns made out of animal horns, ivory, wood, metal or other materials have a wide conical inner bore and can usually produce only a single note. This note is determined by the length and the bore profile of the tube. In some rare cases, it is possible to produce the fundamental note and several harmonics.
It is however possible to produce a complete harmonic series even beyond the 24th harmonic on longer instruments with a narrower bore profile by changing the lip tension and the pressure of the air blown into the instrument.
By adding different technical devices, the original range of notes can be significantly expanded. By doing this, it is possible to complement the natural notes by chromatic notes, thus facilitating the playing of a complete scale. Modified in this way, these instruments can be played together with other instruments.
In the case of the horns with fingerholes, the instruments were originally designed with holes drilled into the instrument. These were first covered by the fingers, then in the 19th century, also by keys.
Trombones with their mainly cylindrical inner bore have a tube the length of which can be modi fied like a telescope ('slides'). By varying the length of the tube, it is possible to produce different ranges of notes, making it possible to play a chromatic scale.
In the 19th century trombones with valves were also used, especially in military bands.