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
Guitar low B string, Roger McGuinn (of The Byrds and Rickenbacker) uses an octave G string paired with the regular G string as on a 12-string guitar, allowing him to incorporate chiming 12-string elements in standard six-string playing. In 1982 Uli Jon Roth developed the "Sky Guitar", with a vastly extended number of frets, which was the first guitar to venture into the upper registers of the violin. Roth's seven-string and "Mighty Wing" guitar features a wider octave range. The bass guitar (also called an "electric bass", or simply a "bass") is similar in appearance and construction to an electric guitar,