String harmonic tap the fifteenth fret, as . Tap harmonic is a technique used with fretted string instruments (usually guitar). It is executed by tapping on the actual fret wire, most commonly at the 12th fret, but also can be executed by tapping any of the fret wires with proper technique. It can also be done by gently touching the string over the fret wire instead of tapping the fret wire if the string is already ringing. See also: Shred Guitar. This technique is used by effect devices producing a magnetic field that can agitate fundamentals and harmonics of steel strings. There
Multi-neck guitar 6-string neck on the bottom and an "octave guitar" for the top neck. This was a 6-string neck tuned an octave higher than the standard guitar, that both extended the range of the instrument, and allowed Maphis to play mandolin-like sounds. Between 1958-1968, Gibson made an instrument of this type which it called the "Double Mandolin" (Gibson EMS 1235). Hybrids with a 6-string guitar neck and a true 8-string mandolin neck were also made (e.g., the 1971 Dawson Electric guitar/mandolin). And Led Zeppelin's John Paul Jones has a triple-neck electroacoustic instrument, custom made for him by luthier Andy Manson, which