(fret) buzz

Fret buzz occurs when a string touches the fretboard or other frets above the picked fret. This can result from too low action, wear and tear of strings, too deep notches in the nut, or misplaced frets.

It can, however, also be caused by playing the instrument in a wrong way. Fernando Sor observes:

For my own part, when I have heard a string jar, I have examined first whether the fault proceeded from the bad conformation of the instrument or from my ignorance in using it; secondly, whether the false direction which I might have given to the play of the right-hand finger was the cause of it, or whether by pressing that string with the left-hand, the force of the arm might not have added to that produced by the pressure of the fingers against the thumb, and, in consequence, the finger-board or neck having yielded backward, brought the string too near the frets. Very frequently I have found it proceed from one of these two causes, and I have endeavoured to correct myself of what I considered a fault.1)

Fernando Sor: Sor's Method for the Guitar. Transl. A. Merrick. London [1832], p. 9