especially in the low register.photo 1 The Ernie Ball company describes Ball's design as "an idea before its time"; the instrument was little used in acoustic musical performances until the late 1980s, when the acoustic basses were used in performances on the MTV Unplugged television program. The Earthwood was quickly supplanted by the Washburn AB-40 designed by Mick Donner and Richard Siegle. The AB-40 and the more affordable AB-20 became the instrument of choice for bass players appearing on Unplugged. Folk bass player Ashley Hutchings used the acoustic bass guitar with his Etchingham Steam Band in 1974 and 1975. An early user of the acoustic bass guitar in rock was English multi-instrumentalist and composer Mike Oldfield, who had one custom-built for him by luthier Tony Zemaitis in the mid-1970s and used the bass on a number of his recordings from that time onwards, a prominent example being his 1975 album Ommadawn. Construction and tuning Unlike the electric bass guitar, which is generally a solid body instrument, the acoustic bass guitar usually has a hollow wooden body similar to (though usually somewhat larger than) that of the steel-string acoustic guitar. The majority of acoustic basses are fretted, but some are fretless instead. Semi-fretted versions also exist, although they are quite rare. Like the traditional electric bass and the double bass, the acoustic bass guitar commonly has four strings, which are normally tuned E-A-D-G, an octave below the lowest four strings of the 6-string guitar. Like the electric bass guitar, models with five or more strings have been produced, although these are less common. In part, this is because the body of an acoustic bass guitar is too small to produce a resonance of acceptable volume at lower pitches on the low "B" string. One solution uses the five string acoustic bass to add an additional high string ("E-A-D-G-C") instead of adding a low "B". Another solution is to rely on amplification to reproduce the low "B" string's notes, or by making the body a little bit larger. There are also semi-acoustic models, fitted with pickups, for use with an amplifier. The soundbox of these instruments is not large enough to amplify the sound. Instead, it produces a distinctive tone when amplified, similarly to semi-acoustic electric guitars. Thin-body semi-acoustic basses such as the violin-shaped Höfner made famous by the early Beatles and several Fender models are not normally regarded as acoustic basses