Breath Support in singing seems like it should be obvious...
The more air that is flowing over the vocal cords, the louder the sound will be.
The muscles that hold the vocal cords together need to be strong enough to withstand the air pressure. That's where the Voice Building exercises come in (if you haven't seen the YouTube Singing Lesson, Click Here)
You want as much air as possible passing over the vocal cords...It's like the difference between a trickle of water slowly flowing out of a faucet, verses a fire hose that is consistently blowing water out of the opening.
You have to be willing to let the air out
You have to be willing to make a loud sound
You have to open the jaw, and let the breath pour out.
Take a breath, and sigh out loudly and quickly. The longer you can let the air flow out, the more "breath support" you have. Time yourself - work on making the air come out for a longer amount of time.
That's about as simple as it is.
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