Abstract: A rotary valve for a musical instrument includes a cylindrical casing having a sidewall closed at opposite ends thereof, and a rotor mounted within the casing for rotation between unoperated position, in which the main tubing is connected to a further tubing portion, and an operated position, in which a length of extension tubing is connected into the air passageway through the instrument, the rotor including a hollow shell member and rotor primary and secondary airway tubes mounted within the rotor shell member for selectively communicating input and output ports of the valve as the rotor is rotated between its unoperated and operated positions, and a plurality of vent openings in the cylindrical sidewall of the rotor shell member for providing pressure relief areas for air directed into the rotor during rotation of the rotor between its unoperated and operated positions.