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
Rhythm game accessories existing "Rock Band 2" drum sets. For the pro guitar mode of "Rock Band 3", a pro guitar controller is required. Unlike standard guitar controllers, pro guitars allow input of any fret/string combination, allowing accurate simulation of a real guitar. The Fender Mustang Pro Guitar controller, which is based on the Fender Mustang, has 102 buttons along its neck which simulate holding the guitar strings against the fretboard. All six strings are represented along 17 different frets. In order to simulate picking/strumming, the Mustang pro controller features a "string box" located on the body of the controller (around the position