Abstract: A dual rotor axial-flow rotor valve structure includes a rotor valve seat for rotatably receiving rotatable first and second rotor valves. The rotor valve seat has a first and a second extension sections connected to end sections of a second and a first tuning slide assembly s. The first rotor valve communicates with end sections of first and second flow passages with a mouthpiece and the other end of the second tuning slide assembly and communicate the other end of the second flow passage with the first or second extension section. The second rotor valve communicates ends of the first and second flow passages with the other end of the first tuning slide assembly and a main tuning slide assembly and communicate the other end of the second flow passage with the first or second extension section.