Took me 3 months to learn overtones, but once you learn, you won’t forget. I started with Tuvan throat singing though and I guess that was the hardest way to learn. But I can do hoomei, some kargyraa, and a little sygyt finally now after 8 months of near daily practice. Alex Glenfield has many very helpful videos if anyone wants to learn. https://youtu.be/D5J5Bc2-SlU?si=wgeYiQEg-UUQC67a