What is the tuba's actuator?

The tuba's actuator refers to the valve system that controls the flow of air through the instrument. Typically, this system consists of three to six valves that the player presses to change the pitch by altering the length of the tubing. When a valve is activated, it reroutes the air, allowing the musician to play different notes. Essentially, the actuator enables the tuba to produce a wide range of sounds and pitches.