The Irish bouzouki (Irish: búsúcaí) is an adaptation of the Greek bouzouki (Greek: μπουζούκι). The newer Greek tetrachordo (4 courses of strings) bouzouki was introduced into Irish traditional music in the mid-1960s by Johnny Moynihan of the folk group Sweeney's Men. Alec Finn, first in the Cana Band and subsequently in De Dannan, introduced the first more-traditional Greek trichordo (3 course) bouzouki into Irish music.
In the early 1970s, Andy Irvine gave his Greek bouzouki to Dónal Lunny, who replaced the octave strings on the two lower G and D courses with unison strings, thus reinforcing their lower frequencies. Soon after, on a visit with Irvine to the workshop of luthier Peter Abnett, Lunny commissioned a bouzouki to the specifications of a classic, 4-course Greek bouzouki but with unison strings and a three-piece, partially staved back. Since then, the instrument has been adapted for Irish traditional and other styles of folk music.
By far the most common tuning for the Irish bouzouki is G2 D3 A3 D4. This was pioneered by Johnny Moynihan (apparently in an attempt to replicate the open, droning sound of Appalachian "clawhammer" banjo) first on the mandolin and then transferred to a Greek bouzouki. It was later picked up by Andy Irvine and Dónal Lunny, and quickly became the next thing to a standard tuning for the 4 course instrument. Other tunings used, although by a minority of players, are "octave mandolin" tuning G2 D3 A3 E4, and "Open D" tuning A2 D3 A3 D4. "Open G" G2 D3 G3 D4, is used by some players and has proven useful for "bottleneck" slide playing. The G D A D tuning is closer to the D3 A3 D4 tuning of the Greek trichordo bouzouki than is the guitar-like tuning C3 F3 A3 D4 used on the modern Greek tetrachordo, and is particularly well suited to a modal harmonic approach to accompaniment as used in Irish traditional music. Alec Finn, playing a Greek trichordo bouzouki, uses the traditional D3 A3 D4 tuning with the octave pair on the low D course changed to unison
For many builders and players, the terms "bouzouki", "cittern", and "octave mandolin" are more or less synonymous. The name cittern is often applied to instruments of five courses (ten strings), especially those having a scale length between 20 and 22 inches (500mm and 550mm). They are also occasionally called "10 string bouzoukis" when having a longer scale length. The fifth course is usually either a lowest bass course tuned to C2 or D2 on an instrument with a long scale, or a highest treble course tuned to G4 or A4 on a shorter scale. Luthier Stefan Sobell, who coined the term "cittern" for his modern, mandolin-based instruments, originally used the term for short scale instruments irrespective of the number of their strings, but he now applies "cittern" to all 5 course instruments irrespective of scale length, and "octave mandolin" to all 4 course instruments, leaving out bouzouki entirely. Mandolin-family luthiers producing an octave mandolin are more likely to use mandolin tuning machines and reproduce the details and styling of their American-style carved top mandolins. Some luthiers choose to refer to their clearly bouzouki-style instruments as octave mandolins, or even as mandocellos, despite the GDAD tuning. The octave mandolin is usually regarded as having a shorter scale length than the Irish bouzouki, in the vicinity of 20 to 23 inches (50 to 59 cm), while the scale length of the Irish bouzouki most often ranges from 24 to 25 inches (60 to 65 cm). Some instruments have scales as long as 26 or even 27 inches (66 to 68 cm). These longer-scaled instruments are generally acknowledged to possess greater volume, sustain, and tonal richness but some players find the stretches involved in fingering too difficult and so prefer shorter scale lengths.
The Octave Mandolin is a fretted string instrument with four pairs of strings tuned in fifths, G, D, A, E (low to high), an octave below a mandolin. It is larger than the mandola, but smaller than the mandocello and its construction is similar to other instruments in the mandolin family. Usually the courses are all unison pairs but the lower two may sometimes be strung as octave pairs with the higher-pitched octave string on top so that it is hit before the thicker lower-pitched string. Alternate tunings of G, D, A, D and A, D, A, D are often employed by Celtic musicians. The names of the mandolin family instruments vary between Europe and the United States. The instruments that are known in the USA as the mandola and the octave mandolin tend to be known in Great Britain and Ireland as the tenor mandola, the octave mandola (or the "Irish bouzouki"). Also, octave mandola is sometimes applied to what in the U.S. is a mandocello. In Europe outside the British isles, mandola is the larger GDAE tuned instrument while the smaller CGDA tuned one is known as alt-mandoline (i.e., alto mandolin), mandoliola or liola. This geographic distinction is not crisp, and there are cases of each term being used in each country. Jimmy Moon, a Scottish luthier calls his version of the instrument by both names and Paul Shippey, an English luthier, uses the term octave mandolin. Confusion will likely continue as the terms continue to be used interchangeably.
Octave mandolin construction is similar to the mandolin: the body may be constructed with a bowl-shaped back according to designs of the 18th-century Vinaccia school, or with a flat (arched) back according to the designs of Gibson Guitar Corporation popularized in the United States in the early 20th Century. The scale of the octave mandolin is longer than that of the mandolin, and varies more widely, from 19" (48.4 cm) to 24" (61.0 cm), with 21" (53.3 cm) being typical. The internal bracing is similar to the mandolin and mandola, with a single transverse brace on the top just below the oval soundhole. On modern instruments X-bracing is sometimes used. As is typical of the mandolin family, octave mandolins can be found with either a single oval soundhole or a pair of "F" soundholes. As with the scale length, the number of frets on an octave mandolin also varies widely, from as few as 17 to as many as 24 frets: 18 or 19 frets is typical.