In the age of steam, the steam calliope was particularly used on riverboats and in circuses. In both cases, a steam supply was readily available for other purposes. Riverboats supplied steam from their propulsion boilers. Circus calliopes were sometimes installed in steam-drive carousels, or supplied with steam from a traction engine. The traction engine could also supply electric power for lighting, and tow the calliope in the circus parade, where it traditionally came last. Other circus calliopes were self-contained, mounted on a carved, painted and gilded wagon pulled by horses, but the presence of other steam boilers in the circus meant that fuel and expertise to run the boiler were readily available. Steam instruments often had keyboards made from brass. This was in part to resist the heat and moisture of the steam, but also for the golden shine of the highly polished keys.