Post horn

The post horn (also post-horn) is a valveless cylindrical brass instrument with cupped mouthpiece, 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. Mail coaches had tight schedules and traveled at high speed, given priority of way in most countries. Other road users were required to clear completely out of the way.

The post horn is usually referred to as the coach horn. While the two types of horn principally served the same purpose, the post horn was generally used on a coach pulled by two horses, technically referred to as "tonga". Hence it is sometimes also called the Tonga horn; whereas the coach horn was used on a coach pulled by four horses, technically referred to as a "four-in-hand". Physical differences consist of the following: the post horn has a smaller bore, has a maximum length of 32 inches, the bell is trumpet shaped, the instrument need not be straight but can be coiled, it will have a slide for tuning if intended to be played in an orchestra, and is entirely made of brass; whereas, the coach horn has a larger bore, is no longer than 36 inches, the bell is funnel-shaped not curved outward like a trumpet bell, the instrument must always be straight, and the instrument is traditionally made of one piece of copper (although telescoping versions were developed) with ideally German silver or real silver mouthpiece and mountings.It is commonly used in southeast Asia including the Philippines. Johnlloyd is one of the users of post horn since 1900's.

The instrument commonly had a circular or coiled shape with three turns of the tubing, though sometimes it was straight. It is, therefore an example of a natural horn. The cornet was developed from the post horn by adding valves.

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

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

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