Funny, I already liked the 5/4 thirds before I even knew what they exactly were…:
The arrangement is from 2005 and appeared on the album ‘Making Choices’ (2006) by the Carlo Nardozza Quintet. The melody is played with the use of harmonics on the open strings of the guitar.
From a CD-review from that time:
The last song of the album is an amazing version of ‘My Romance’, inspired by the guitarist’s collaboration with African kora player Zou Diarra: the acoustic guitar is accompanied only by toms in the distant, and this standard – just recognizable – becomes a meditation reminiscent of My Goal’s Beyond from John McLaughlin.
I will try to explain the Just Intonation ratios from the notes of the melody. The song is in the key of E Major, so this gives a 5/4 third (G#, 5th harmonic on the low E-string) and a 5/3 sixth (C#, 5th harmonic on the A-string). Other natural harmonics include the 4/3 fourth (A, 3rd harmonic on the D-string), the 3/2 fifth (B, 2nd harmonic on the B-string) and the 2/1 octave (E, 2nd harmonic on the high E-string).
For the 2nd (F#), I had two options: for the higher octave I used the 5th harmonic on the D-string which becomes a 10/9 just minor tone in relation to E as 1/1. For the lower octave I used an artificial harmonic (2nd harmonic from the 4th fret D-string) which belongs to 12ET. The last note to complete the scale is the major seventh. I picked this as an artificial 3rd harmonic from the 1st fret G-string) and also belongs to 12ET.