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
Eleven-string alto guitar 11-string alto guitar. This design introduced two main elements. The first was to provide conventional lute tuning by tuning the first six strings a minor third higher (hence the name "alto guitar"). It is equivalent to putting a capo on the third fret of the normal prime guitar. The second element was to add five extra strings to accommodate low notes. The typical 11-string alto guitar tuning is (from low to high strings): Bb1 C2 D2 Eb2 F2 G2 C3 F3 Bb3 D4 G4. Current luthiers who build 11-string alto guitars, primarily located in Sweden, include Heikki Rousu and Roger