string 5 between frets 10 formed on the surface of the fingerboard 9 in a string taut direction is depressed and urged against the surface of the fingerboard 9 a corresponding fret switch fsw is turned on string trigger switches tsw are housed in the string trigger switch unit 7 and the strings 5 are connected to the string trigger switches tsw when the string 5 is picked or finger plucked a corresponding string trigger switch tsw is turned on thereby generating a musical tone the fret switches fsw embedded in the fingerboard 9 at portions between the frets 10 are arranged as shown in fig2 that is the fret switch fsw comprises a printed circuit board 12 and a rubber sheet 13 fitted in a recess portion 11 formed in the upper surface of the neck 3 i e the fingerboard 9 the rubber sheet 13 is stacked and adhered on the printed circuit board 12 both ends of the rubber sheet 13 are bent in a u shape to hold both ends of the circuit board 12 thereby fixing the circuit board 12 contact recess portions 14 are formed at a position corresponding to each string 5 on the lower surface of the rubber sheet 13 in contact with the upper surface of the circuit board 12 in this case as shown in fig3 n arrays if the number of strings is six as in a guitar the total number of fret arrays is 6n of the contact recess.