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 traditional music form of improvised "countermelody" is often used in the accompaniments of bouzouki and guitar players. In contrast to many kinds of western folk music, there are no set chord progressions to tunes; many accompanyists use power chords to let the melody define the tonality or use partial chords in combination with ringing drone strings to emphasize the tonal center. Many guitarists use DADGAD tuning because it offers flexibility in using these approaches, as does the GDAD tuning for bouzouki. Like all traditional music, Irish folk music has changed slowly. Most folk songs are less than 200 years old. One measure