New double bass strings may include a short and thin (about 1 centimeter long) section of a plastic tube. It's the D string which goes through the tube. What is it, the tube? What is one supposed to do with the tube when installing the strings?
The tube shown on the detail of a tailpiece arrived with this same (new) instrument already stringed with these same Spirocore strings, but by that time, it was placed within the bridge groove of this same D string, as if saying "I'm not properly setup, take me to the luthier."
