Many wind instruments require a continuous breath. The Didgeridoo is one example. Not all songs require circular breathing, but it is basically a technique that allows for continue breathing while playing.
How to Do Circular Breathing Technique
- Inhale fully
- Exhale and Blow
- Before next breath, Continue with Cheeks
- Quickly Breathe in through the nose while Cheeks exhale
There are several records/musicians who can play a note or continuously for almost 1 hour.
Read more about Circular Breathing