Many people have an artist that really touches them in profound emotional ways. Some times such an artist is able to bring people to tears. For guitar wizard extraordinaire Steve Vai it is Tom Waits.
In an interview with Wikimetal, Vai says:
"My favourite artist right now is Tom Waits. I never go anywhere without everything he's ever recorded. There are some of his songs that I can't listen to in public because I start uncontrollably weeping. There's something about his voice, his music. He's just so connected and unique. I think he's the greatest American artist because he captures an intention and he makes you feel it, if you're connected with it."
It's quite understandable for Vai to lose it at Tom Waits because the dude really does have one hell of a soulful voice and has some prolific lyrics. It isn't the most powerful or dynamic, but it has passion and authenticity to it that many other performers just don't seem to have. Kind of interesting though that someone so focused on guitar like Vai would be into such music, but then again I guess inspiration comes from more than one place.