At about 40 seconds into this video:, Karene stops using the bass buttons and starts playing the treble side only when opening the bellows. Furthermore, in order to do so, she manages to close the bellows very quickly at her chosen moments without making any sound. So my question is: How? She is not using the air release button. That's clear, because you can see her thumb, which is nowhere near the air release button, and the air release is in the usual place on the back (which can be seen in other videos where she plays the same accordion).
It looks like she might be mashing a bunch of bass buttons all at once when she's closing the bellows. But I have tried that on my own accordion, and while it does let the bellows close a little more quickly, of course, it still makes an awful sound -- and a very loud sound, if I try to close the bellows as quickly as she is closing hers.
ADDENDUM: After posting this question, I became of aware of the Accordionists.info forum, and I managed to find a thread from last November that discussed this "play only on the draw" technique. There was a back and forth discussion about it among 3 or 4 people, but no one had an answer as to how it was accomplished.
Just a Side Note: Karene is only 13 years old in this video!