i been watching the G3 live in denver dvd, and i keep watching the same bit in Steve Vai's show over and over. it happens in the song 'Juice' jus before the bass solo. Vai does this strange tapping thing where he taps the neck behind his fretting hand, in a really fast motion. i have no idea what he does, and wanted to know if anyone here did. if i haven't explained it to well, let me know.