Another design consideration for the bass is whether to use frets on the fingerboard. On a fretted bass, the frets divide the fingerboard into semitone divisions, (as on a normal guitar). The original Fender basses had 20 frets, but modern basses may have 24 or more.
Fretless basses have a distinct sound, because the absence of frets means that the string must be pressed down directly onto the wood of the fingerboard. The string buzzes against the wood, as with the double bass, creating a "mwaah" sound. The fretless bass allows players to use the expressive devices of glissando, vibrato and microtonal intonations such as quarter tones and just intonation. Some bassists use both fretted and fretless basses in performances, according to the type of material they are performing. While fretless basses are often associated with jazz and jazz fusion, bassists from other genres use fretless basses, such as metal bassist Steve DiGiorgio. The first fretless bass guitar was made by Bill Wyman in 1961 when he converted an inexpensive Japanese fretted bass by removing the frets. The first production fretless bass was the Ampeg AUB-1 introduced in 1966, and Fender introduced a fretless Precision Bass in 1970. In the early 1970s, fusion-jazz bassist Jaco Pastorius created his own fretless bass by removing the frets from a Fender Jazz Bass, filling the holes with wood putty, and coating the fretboard with epoxy resin.
Some fretless basses have "fret line" markers inlaid in the fingerboard as a guide, while others only use guide marks on the side of the neck. Tapewound (Double Bass Type) strings are sometimes used with the fretless bass so that the metal string windings will not wear down the fingerboard. Some fretless basses have fingerboards which are coated with epoxy to increase the durability of the fingerboard, enhance sustain and give a brighter tone. Although most fretless basses have four strings, five-string and six-string fretless basses are also available. Fretless basses with more than six strings are also available as "boutique" or custom-made instruments.
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