circular breathing or atleast i think that is how you spell it
i can blow a steady stream of air into a glass of water for 10 minutes but when i puff up my face to inhale with my nose i lose my sound?

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what i mean is that when i try and do it on the trombone i cant do it but i can do it with a glass of water or a recorder

What the heck IS circular breathing?

I'm not to the point of circular breathing on tuba, trombone, or bassoon but i know a little about it. Basically you play a note and before you run out of air you breath through your noise and continue the air stream. If I remember correctly this is a needed technique for oboe, and a useful technique for bassoon and other instruments. Along with a good buzz, proper breathing methods, and lung capacity this will let you play more while taking less breaths from your mouth.

(i'm sleepy, i'm sorry if this post is gibberish)