Guitar Frets are laid out to accomplish an equal tempered division of the octave. Each set of twelve frets represents an octave. The twelfth fret divides the scale length exactly into two halves, and the 24th fret position divides one of those halves in half again. The ratio of the spacing of two consecutive frets is formula_1 (twelfth root of two). In practice, luthiers determine fret positions using the constant 17.817—an approximation to 1/(1-1/formula_1). If the nth fret is a distance x from the bridge, then the distance from the (n+1)th fret to the bridge is x-(x/17.817). Frets are available in
Eight-string guitar and six-string variants. The standard tuning (from low to high) is F#, B, E, A, D, G, B, E. Many prefer to tune the F# to a low E (E1), the same note as the lowest string on a four-string electric bass in standard tuning, and providing the guitar with a fuller sound by having three different E strings. Like the seven-string, the first mass-produced eight-string guitar was made by Ibanez guitars in Japan; the RG2228. The main design issue faced with an eight-string guitar is tuning stability with the lower strings. This is due to the neck being constructed