First I'd like to thank you for helping to shape many of my favorite records!
I've always loved the album Ziggy Stardust. There are so many little interesting tidbits once you really listen closely. I saw on your discography that you were producer on this album.
Both Moonage Daydream & Velvet Goldmine feature backing vocals in the form of DB humming bass notes during the choruses. These backing vocals give these songs a very unique quality. Almost a Gregorian chant behind rock music.
Could you please tell me more about these? How was this achieved (i.e. how many voices?, lots of reverb?) What was the inspiration for this? Was this your idea or perhaps David's or Mick's?