I certainly consider vai as one of the most creative musicians in the world. But there is this technique he uses in a lot of songs that i can't figure out. I've seen it work like this:

He inverts hand and puts his right hand on the beginning frets before the left hand which is nearer the bridge,also on the frets. Right at that time he taps at a extreme speed. My question is, what's the name of this thing? Does he actually do something with his right hand?

I've seen him do it in Bad Horsie Live, in Tender Surrender live, and in Crossroads right in the solo where he thinks he has beaten ry cooder.

Thanks in advance