180. The panduri-tambouras (F2:F2)-(D3:D3)-(A3:A3)-(E4:E4) (6M-5-5) tuning of a 4-courses instrument.

It is a combination of tuning that requires intervals of 3 or inverted by 6, that give easy major-minor triads and at the same time the tuning by 5's (or Bouzouki 5-4).

For a 4-courses instrument like Bouzouki etc it can be with a slight inversion in the lower triad chords E.g.

(E2:E2)-(C3:C3)-(G3:G3)-(D4:D4)  (6M-5-5)

OR

(F2:F2)-(D3:D3)-(A3:A3)-(E4:E4)   (6M-5-5)

(if used to tambouras or mandolin)

Or if we are used to Bouzouki (which is also open D minor)

(F2:F2)-(D3:D3)-(A3:A3)-(D4:D4)   (6M-5-4)

The only reasons that one would prefer the later from the former is that the (A3:A3)-(D4:D4)  allows for easy two notes chords by intervals of 3. Nevertheless, it loses its uniformity for solos in the higher 3 strings, and also some major-minor triads on them playable at 2 or 3 frets. Personally, I would prefer the

(F2:F2)-(D3:D3)-(A3:A3)-(E4:E4)   (6M-5-5)

The 5 main advantages for HARMONIC AND MELODIC IMPROVISATION  of this tuning are:

1) It allows for the ancient isocratic accompanying of fast melodies with an interval of  5 by the two immediate lower strings of the string of the melody in the   -5-5 part

2) The 2-octaves 7-notes scale by alternating intervals of 3 that shape the triad chords in a diatonic scale (called also melodic corridor or wheel by 3rds see post 94 and 79  )  have symmetric representations in this tuning in the  -5-5 part .

3) It is uniform tuning for melodies to shift among the strings in the   -5-5 part .

4) The shift higher or lower by an interval of 4 or 5 vertical to  strings  which is usually a  mutation of a melodic theme played horizontally on a string  is very easy and symmetric in the higher 3 strings

5) It allows for both melodic improvisation with isocratic accompanying by intervals of 5 and harmonic improvisation with easy to play in 1 or 2 frets major-minor triads in the lower 3 strings.

6) It allows strumming only