In an electric guitar, the sound produced upon playing on a string thrown, to a predetermined tension, along and over the fingerboard between the bridge and the head is checked by ear to determine phantom semitone frets with the fingerboard extended imaginarily toward and closer to the bridge and the pickup is mounted on the body at one of the phantom semitone frets. The determination of the installation position for the pickup by reference to vibrations of the string on the basis of the above principle of phantom frets not only assures an improved reproducibility of guitar sounds but enables one to obtain nearly infinite and original sounds from the electric guitar.