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
Bouzouki one piece. The top plays a major role in the sound because it resonates and strengthens and prolongs the vibration of the strings. Another factor that affects the quality of the sound is the varnish and the method of its application. The best varnish is a natural one made of shellac, which is applied by hand in many layers in the traditional way, for both acoustic and visual effect. The neck must be of very dry hardwood in order not to warp and increase the distance of the strings from the fret board (the action height) which makes playing the