Kaba "register" harmonics on Kaval

[buha]

I think the following video shows pretty well what happens when you blow in such a way in a Kaval as to obtain (what they call) the Kaba register sound versus normal 2nd register sound.

https://www.youtube.com/shorts/XFuaekD16yQ

You can see how the lowest harmonic, from 1st register, ~313 Hz (D#4 311) comes up depending on how I blow.
The permanent note here is the ~627 Hz (D#5 622)in 2nd register.

Interesting to note how the rest of the harmonics change when the D#4 comes up.

Kaba is very hard for me, I can't really control it well, and I noticed that when I can't produce it, it's because the two notes aren't exactly at double frequency. This must have something to do with the different air jet in the 2 registers and also with the end corrections being a function of frequency.

I am going to explore how could I improve my instrument to make Kaba more easier to play but until then let me have your comments, curious if there are other people interested in this.

[buha]

I updated the link, it was broken.