lol – the snake joke!
If you are doing JF’s altissimo course, the 1st three overtones you should be able to do.
I found the 7th, 6th & 5th overtone the next easiest to do and the 4th overtone was a right pig on my sax.
I also found the higher overtones on the low D much harder compared to the low Bb overtones.
Once you get the 1st three overtones on all 5 Low keys, then try and go for the Altissimo A, which i found easier
than the Altissimo G. in my case i was doing the altissimo G,G# and A before i could do the higher overtones.
Then by practicing lots of chromatic runups – i started to get the rest of the overtones all at once on the low Bb.
If you hear any high pitched noises on the low Bb, check with a tuner as these are normally the higher overtones.