Irish bouzouki 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. The original Greek bouzouki was a three course/six-string instrument ("trichordo"). In the 1950s, a four course/eight-string ("tetrachordo") version was developed. The newer "tetrachordo" bouzouki
Irish bouzouki and a flat back with straight sides replaced the round, stave-built back of the Greek bouzouki. English builder Peter Abnett, who was the first instrument-maker to build a uniquely "Irish" bouzouki – for Dónal Lunny in 1970 – developed a hybrid design with a 3-piece partially staved back and straight sides. All of the initial Irish bouzoukis had flat tops, but within a few years a few luthiers such as Stefan Sobell began experimenting with carved, arched tops, taking their cue from American archtop guitars and mandolins. Even so, today the overwhelming majority of builders continue to opt for flat