The Bouzouki is a Greek long-necked lute, now also found in Ireland as the "Irish Bouzouki". Up to the 19th-century the Greek bouzouki was indistinguishable from the Turkish saz with its carved wood resonator, movable gut frets and wooden tuning-pegs. By the end of the 20th century it was exclusively round backed, with fixed metal frets and metal machine tuning-heads. In contrast, the modern Turkish Saz has retained its movable frets and violin like tuning pegs.
The instrument has three or four double courses of metal strings tuned ebe' and dgbe' respectively and is played with a plectrum. The version with four courses of strings has developed since World War II.
In Greece, during the first half of the 20th century the bouzouki was used principally for playing Rebetika music. Traditionally the bouzouki with three courses was thought to be unsuitable for playing chords while four course version opened up the possibility of playing Western-style chords.
In the late 1960s traditional Irish musicians such as Johnny Moynihan and Donal Lunny who were involved in the folk revival in Ireland adopted the bouzouki, tuning it more like a fiddle but an octave lower. In a similar manner they adopted the “Irish” Tenor banjo from America also tuning it GDAE like the fiddle. This made it easier to play standard fiddle tunes in their standard keys.
Bands such as Sweeney's Men, Planxty and the Bothy band were among the first groups to use the instrument in Irish music, initially to accompany traditional folk songs and later to provide accompaniment for traditional Irish dance music. The tuning of the Instrument was g’d’a’d’ or g’d’a’e’, an octave below the mandolin and fiddle. Some players use octave strings on the 2 lower courses like a 12 string guitar. There are other tunings that are not as common.
Irish Bouzouki players prefer either short scale instruments or long scale instruments as a matter of preference. The short scale instruments are easier to use for melody playing, while the long scale instruments, because of the ability to use lighter strings, have a fuller sound for use in chordal accompaniment. The longest scale instrument being made as a production model is the imported Trinity College Irish Bouzouki. Modern Irish Bouzoukis are built with a flat back, instead of the traditional round back. Mandocellos can also be used as long neck Bouzoukis simply by changing the string gauges and tuning.