Circular breathing is a special technique utilized primarily by players of the didgeridoo (and some other wind instruments) in order to continuously blow air out of the mouth. Many jazz musicians utilize some form of circular breathing. For example, Kenny G, who held the world record for holding a single note (E) for 45 minutes and 47 seconds on his soprano saxophone.

Circular breathing is a special technique utilized by players of some wind instruments used to produce a continuous tone without break, accomplished by the use of the cheeks as a reservoir of air while breathing through the nose rather than the mouth. The technique is used extensively in the playing of the Australian didgeridoo and the Sardinian launeddas, as well as many traditional oboes and flutes of Asia and the Middle East. A few jazz and classical wind players also utilize some form of circular breathing. Although many professional wind players find circular breathing highly useful, few pieces of music composed before the 20th century actually require its use. A notable exception would be "Moto Perpetuo" as transcribed by Rafael Méndez from Paganini. Trumpeters playing this piece have to have full control of their circular breathing in order to play the piece as intended. Kenny G is perhaps the world's most famous circular breather, setting a world record for holding a single note for 45 minutes. The basic method is as follows: The person inhales fully and begins to blow. Once the lungs are nearly empty, the last volume of air is blown into the mouth, and the cheeks are inflated with this air. Then, while still blowing this last bit of air out by allowing the cheeks to deflate, the person must very quickly fill the lungs by inhaling through the nose prior to running out of the air in the mouth. If done correctly, by the time the air in the mouth is nearly exhausted the person can begin to exhale from the lungs once more, ready to repeat the process again. Physiologically, the process is similar to drinking at a water fountain and taking a breath of air while water remains in the mouth, without raising the head from the water stream. The body "knows" to not allow water into the lungs. It is this same instinct that a circular breather taps to play their instrument. http://en.wikipedia.org/wiki/Circular_breathing

Circular breathing is very wicked hard technique. It involves breathing in through your nose while breathing out through your mouth while playing...I can't do it. I would be great if I could...no breath pauses in music!