Philipp Fahrbach's method book

For 2-key ocarina going up to G. In German.

It has an unusual focus on intervals as what you should learn first.

It is interesting how the fingering chart this method book seems to imply that one should support the ocarina on the high notes by putting most of the right hand fingers below the instrument, I have never seen anyone using such a technique.

I like the way that the method book teaches intervals from the start. I think intervals first is a better approach because it teaches the muscle memory needed to move between all notes on the instrument effectively. That removes the need to consciously think about which individual fingers to move.

Intervals first is similar to how I teach.