You may think this instrument is a tuba, but it's not! It's a smaller version called a Euphonium.

Here is the Euphonium with its larger cousin, the Tuba

David Childs, one of the best Euphonium players in the world, plays a piece called "Czardas."

There is a different type of Baritone Horn made for Marching Bands that are held more like trumpets. Check out a demonstration of a marching Baritone in this clip, as he plays the theme song to the show "Arthur."