The tenor guitar or four-string guitar is a slightly smaller, four-string relative of the steel-string acoustic guitar or electric guitar. The instrument was initially developed in its acoustic form by Gibson and C.F. Martin so that players of the four-string tenor banjo could double on guitar. Construction Tenor guitars are four-stringed instruments normally made in the shape of a guitar, or sometimes with a lute-like pear shaped body or, more rarely, with a round banjo-like wooden body. They can be acoustic, electric or both and they can come in the form of flat top or archtop wood-bodied, metal-bodied resonator, or solid-bodied instruments. Tenor guitars normally have a scale length similar to that of the tenor banjo and octave mandolin of between . History and development The earliest origins of the tenor guitar are not clear, but it seems unlikely that a true four-stringed guitar-shaped tenor guitar appeared before the late 1920s. Gibson built the tenor lute TL-4 in 1924, which had a lute-like pear-shaped body, four strings and a tenor banjo neck. It is possible that similar instruments were made by other makers such as Lyon and Healy and banjo makers, such as Bacon. In the same period, banjo makers, such as Paramount, built transitional round banjo-like wood-bodied instruments with four strings and tenor banjo necks called tenor harps. From 1927 onwards, the very first true wood-bodied acoustic tenor guitars appeared as production instruments made by both Gibson and Martin. Almost all the major guitar makers, including Epiphone, Kay, Gretsch, Guild and National Reso-Phonic, have manufactured tenor (and plectrum) guitars as production instruments at various times. Budget tenor guitars by makers such as Harmony, Regal and Stella, were produced in large numbers in the 1950s and 1960s. National, formed by the Dopyera Brothers, also made significant numbers of resonator tenor and plectrum guitars between the 1920s and 1940s. Dobro, another company associated with the Dopyera Brothers, as well as National, also built various resonator tenor guitar models. In 1934, Gibson introduced an acoustic archtop tenor guitar, the TG-50, based on the acoustic archtop six-string model, the L-50, with its production run lasting until 1958. In 1936 Gibson introduced the world's first commercially successful electric Spanish-style guitar, the ES-150. In early 1937 Gibson also began shipping two other versions of the ES-150: a tenor guitar (the EST-150, with four strings and a 23" scale, renamed the ETG-150 in 1940) and a