Just intonation is interesting, but it sort of explodes the composition complexity, because for each note the next (or concurrent) note can be based either on some root note or the current note. For example going up major thirds in C would be C-E-G#, but with just intonation you have to make the choice if that last note should be (C * 5/4) * 5/4 , or C * 8/5. The magic of equal temperament makes the distinction go away, so things are simpler.