to get back to dadgad and other tunings with a one tone interval, the point is that if you are going to use the instrument for accompaniment rather than playing melody on its own, it allows more options and is easier [often]to use dyads or chords that leave out the third of the chord the one that establishes whether it is major or minor, it al;so makes it easier to use for example a d that consists of several fifths and roots and even sometimes, while this is possible in standard the options are more limited, however unless you are extremely skilled it is easier to play radtime and tunes that change key or modulate in standard , so dadgad has advantages and limitations. carthy changed from dadgad to the tuning he now uses not only to suit his voice but he reckons if is a little bit more versatile than dadgad