Posthorn

The post horn (also post-horn) is a valveless cylindrical brass instrument with a cupped mouthpiece. The instrument was used to signal the arrival or departure of a post rider or mail coach. It was used especially by postilions of the 18th and 19th centuries.

The post horn is sometimes confused with the coach horn, and even though the two types of horn served the same principal purpose, they differ in their physical appearance. The post horn has a cylindrical bore and was generally used on a coach pulled by two horses (technically referred to as "Tonga"); hence, it is sometimes also called the Tonga horn. The coach horn, on the other hand, has a conical bore and was used on a coach pulled by four horses (referred to as a "four-in-hand"). The post horn is no more than 32 inches in length, whereas the coach horn can be up to 36 inches long. The latter has more of a funnel-shaped bell, while the former's bell is trumpet shaped. Post horns need not be straight but can be coiled – they have a smaller bore – and they are made entirely of brass. A post horn will have a slide for tuning if intended for orchestral settings. It is commonly used in South East Asia including the Philippines. John Lloyd was one of the users of post horn in the 1900s.

The instrument is an example of a natural horn. The cornet was developed from the post horn through the addition of valves. Some uses of the post horn in modern-day culture can be found in folklore and screen plays. Due to the lack of tone controls, the post horn is not usually used as a musical instrument.

In the late 17th century, Johann Beer composed a Concerto à 4 in B♭, which paired a post horn with a corne de chasse as the two solo instruments, accompanied by violins and basso continuo.

Mozart composed his Serenade No. 9, the "Post horn Serenade", in 1779.

Mahler and others incorporated the post horn into their orchestras for certain pieces. On such occasions, the orchestra's horn player usually performs with the instrument. One example of post horn use in modern classical music is the famous off-stage solo in Mahler's Third Symphony. Due to the scarcity of this instrument, however, music written for it is usually played on a trumpet or flugelhorn.

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