Sousaphone

The sousaphone is a type of tuba that is widely employed in marching bands. Designed so that it fits around the body of the tubist and is supported by the left shoulder, the sousaphone may be readily played while being carried. The instrument is named after American bandmaster and composer John Philip Sousa, who popularized its use in his band.

The principle

the sousaphone in principle but has a far narrower bore, and a much smaller bell which points between straight up and to the player's left.

http://en.wikipedia.org/wiki/Sousaphone