Ranking Interval Complexity

Question

I would like to know the order of complexity of musical intervals (in a melody). I learned about this from an exposure to the Kodaly method, although I have not learned from nor taught using the Kodaly method. But in my reading it introduced the concept of how the intervals are naturally learned. Seems like there should be an ordering. I can see that the first two are a minor third down and a perfect fourth up, but I don't know where to find a list of the intervals from easiest to hardest, treating the up direction and the down direction as separate things.

I realize that this ordering of interval difficultly or learning order may be dependent on the culture of the student. It would be extra cool to understand how this ordering of interval difficulty related to the harmonic series, since the first interval there is a perfect fifth up, which does not match my understanding that a minor third down is the easiest interval.

Answer 1

In my experience as a musician and using Kodaly, it's less about the intervals themselves as it is about the notes of the scales used. For instance, a minor third down is represented as "sol mi" and a perfect fourth up is "sol do". You can see how these are the notes of the tonic triad.

Therefore, in ranking the complexity of an interval, I believe it would be more useful to consider which step of the scale it is. So, if the note lies outside of the key, yet is a perfect fifth up, it would be listed as more complex.