Natural trumpet
Overview
 
A natural trumpet is a valveless brass instrument
Brass instrument
A brass instrument is a musical instrument whose sound is produced by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips...

 that is able to play the notes of the harmonic series
Harmonic series (music)
Pitched musical instruments are often based on an approximate harmonic oscillator such as a string or a column of air, which oscillates at numerous frequencies simultaneously. At these resonant frequencies, waves travel in both directions along the string or air column, reinforcing and canceling...

.
The natural trumpet was used as a military instrument to facilitate communication (e.g. break camp, retreat, etc).

Even before the early Baroque
Baroque
The Baroque is a period and the style that used exaggerated motion and clear, easily interpreted detail to produce drama, tension, exuberance, and grandeur in sculpture, painting, literature, dance, and music...

 period the (natural) trumpet had been accepted into Western Art Music. There is evidence, for example, of extensive use of trumpet ensembles in Venetian ceremonial music of the 16th century.
 
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