The Structure of the Bassoon
A Long Tube that can be Separated
Five separate parts
The bassoon is a woodwind instrument made of many joints, but it can be separated into five main parts. After the bocal comes the tenor joint, below which is the double joint, then the bore extends upwards to the bass joint, and the bell joint.
The double joint, through which the bore passes twice
As its name suggests, the bore passes twice through the double joint, which is the part where the bore turns back on itself. As can be seen in the photograph, a cross section of the joint shows its ellipse shape, with the thinner bore section coming from the tenor joint, and the wider tube being the bore section that extends toward the bass joint. Within the wider tube the grain of the wood can be seen, but the entrance to the thinner tube is covered with metal. The interior is black because an ebonite pipe has been inserted for reinforcement and to protect against moisture. Black ebonite pipe has also been inserted at the tenor joint.
The U-tube, where the bore turns back on itself
If we remove the protector cap attached to the bottom part of the double joint, there is a metal U-tube that bulges into an elliptical shape. Above the U-tube, cork packing is inserted. The turn of the U-tube changes the direction of the two bores within the double joint, connecting them so that they form one tube. For this reason, the U-tube has to be made with great precision. Dropping or denting the part is dropped may lead to deterioration in the instrument's sound.
The basson before the U-tub
The U-tube was made by German military bandmaster Almenräder in around 1825. As it happens, the low volume of the French-style basson presented a challenge, and was one reason that the U-tube was not adopted for a long time.