Circular breathing requires good cheek back pressure and a strong core. And it’s a trick of timing and being relaxed. Not easy at first. It took me 3 weeks of blowing into a straw in a glass of water to time when to take the quick inhale of air while at the same time pushing air that I had stored in my cheeks out through a strong squeezing in of the cheeks and my core engaged. Once I was able to do this through a little straw, I then transferred into the didgeridoo.
Circular breathing is a practice. At first I would get one circular breath. Then I wouldn’t be able to do it for a day or two. Then it came back. I could do 2, 3. Gradually, I improved my power and timing of breath so that I could play continuously for a minute, then 5, then 20.
Not all didgeridoos are made equal, obviously. When you learn on a didge that requires a lot of blowing, it’s much harder to learn circular breathing. When you play on a didgeridoo that has incredible back pressure, it’s much easier to learn how to circular breathe.
A good didgeridoo comes down a lot to the mouthpiece. I prefer wooden mouthpieces (not beeswax, that break or change shape or move around). I also have found that my new gourd didgeridoo made by Geoff Frost has incredible back pressure and resonance and is amazing for both sound healing and fast rhythms.
Be patient and keep practicing, and one day you’ll find yourself circular breathing.