A sousaphone is a large brass musical instrument that wraps around the player's body like a massive metal hug. It looks like a tuba that's been bent into a circle, with a huge bell that points forward over the player's head instead of straight up.

The sousaphone was designed specifically for marching bands. Regular tubas are heavy and awkward to carry while walking, but a sousaphone rests on the player's shoulder and curves around their body, making it possible to march and play at the same time. That big forward-facing bell projects the deep, booming bass notes across a football field or down a parade route.

The instrument is named after John Philip Sousa, the famous American composer and bandleader known as “The March King.” In the 1890s, Sousa wanted a bass instrument that could keep up with his marching bands, so instrument makers created this design. When you watch a college marching band perform at halftime, those giant circular brass instruments providing the low, powerful foundation are sousaphones. They typically play the lowest notes in the band, giving marching music its chest-thumping power and helping everyone stay together with a steady beat.