What instrument is brass instrument tubing in circular coil?

The instrument with brass tubing in a circular coil is called a "Trombone." Specifically, the most common type is the slide trombone, which uses a telescoping slide mechanism to change pitch. The circular coil design is typically associated with the more compact form of the instrument, allowing for easier handling and transport. Other brass instruments, like the tuba, also feature coiled tubing but have different playing mechanisms.