A calliope is a sort of steam-powered organ that sounds like a set of tuned teapots.
The boiler inside the machine generates steam, and the pressure makes the shrill whistle sound.
But steam-operated devices sometimes blow up and calliopes were no exception.
To reduce injury as much as possible, they were placed at the end of the circus parade.
A calliope is typically very loud and even small calliopes can be heard for miles around.