Weird :confused: Perhaps he didn't want to be credited ?

http://gothamist.com/2007/07/11/suzanne_vega_mu.php

Beauty and Crime also features Lee Renaldo [Sonic Youth] on one song. How did you end up working with him?
He’s someone I’ve run into for 15 years all over New York and we’ve always been friendly and chatted about working together. So I thought he’d be a good guy to bring in on a couple of songs; he actually plays on two songs.
Is there any chance of him sitting in during any of your New York appearances?
I don’t know; I guess I’ll have to ask him and find out!

http://thephoenix.com:80/article_ektid44992.aspx

“Angel’s Doorway,” the story of a cop on post in the dusty wasteland of the ruined Trade Center, has a turn from another prominent New York City musician: Sonic Youth guitarist Lee Ranaldo. His shimmer and clang gives the song a ghostly element.
“Lee is somebody who I keep running into all over New York, at different parties and events. I thought it would be nice to have him on that song. I was looking for a combination of new sounds, and though what he did wasn’t different for him, it certainly was for one of my songs.”