I tip my hat to
XX for the background info. In modern times, a svengali is someone who pulls strings - a maker of
pop culture successes. Sometimes the
puppets cut the strings, with mixed results. It's usually a
pejorative, but it shouldn't be. Here's some pop svengali links, off the top of my head:
Kim Fowley,
Don Kirshner,
Creed Taylor,
Brian Epstein,
New Edition,
Andrew Loog Oldham... It was
Gil Evans' favorite anagram.