This maybe a stupid question..
Why does it seem like sometimes when I play the flute, it feels alive.. like you can actaully feel the air vibrating against the key. I actaully play better when this happens. But lately I haven't been feeling it.. my flue still makes a nice sound but tends to get really soft.

It means you're getting a really focused sound, congrats. I've noticed the more focused and controlled my sound, the more pronounced the vibration.

When I had braces, each time I would get my braces tightened the vibration would go away. When I found my focus again with the new situation of my teeth, it would slowly come back. God am I glad to be rid of those things...

Yeah thats probably it since I do have braces and they do bother me once in a while. It does get quite frustrating when I'm trying to make the flute vibrate more.. I tend to overblow and play the next harmonic. Well now I know its probably my braces as I didn't have this problem on my old flute when I didn't have braces. Thanks.. can't wait to get the braces off!!!

the same thing happens to me all the time... u see, whenever i can hear that clear crack in the sound, the vibrato tend to be very euphonious...but whenever i cant feel that any more, i find a hard time to really open up the sound...it's troubling me really...

Yes, that's exactly what happens to me. I can't let out a big sound when I don't feel the flute vibrating. I'm hoping it's my braces causing that. It could be the temperature too, but it happens in cold and warm environments.

Yeah, that could be it. My flute's going in for the annual COA soon, so I'll have the tech check it out. Thanks for the advice