Tuning device is a term used to describe any device used to adjust the sound of an instrument. The three crossword solutions for this term are PEG, FORK, and KNOB. A PEG is a small cylindrical piece of wood or metal that is inserted into the holes of a stringed instrument to adjust the tension of the strings. A FORK is a tuning device used to adjust the pitch of a stringed instrument by pressing down on the string at a certain point. Finally, a KNOB is a tuning device used to adjust the volume or tone of an instrument.