| 摘要 |
A trombone has a rotary valve unit inserted between two parts of a main tube and further connected to a bypass tube, and a player manipulates the rotary valve unit for changing the length of vibrating air column, wherein the rotary valve unit has a cylindrical casing connected at both end surfaces thereof to the parts of the main tube, a first pair of ports formed on the side surface thereof and connected to both ends of the bypass tube and a second pair of ports, a short tube connected between the ports of the second pair and a rotor rotatable inside the cylindrical casing and having two air passages spaced from one another in the direction of the rotational axis thereof and connecting one of the parts of the main tube through the short tube to the other part at a first angular position and one of the parts through the bypass tube to the other part so that the rotary valve unit is compact.
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