Known in the US as alto horn, in Germany as althorn, and in the UK as tenor horn, this brass instrument pitched in Eb has a conical bore (gradually widening) and normally uses a deep, cornet-like mouthpiece.

It is most commonly used in marching bands, brass bands and similar ensembles, whereas the horn tends to take the corresponding parts in symphonic groupings and classical brass ensembles.

In the US and Germany the name tenor horn is identical to baritone horn. To avoid confusion, the instrument is also occasionally referred to as Eb horn.