It's got something to do with the Mississipi river. If a radio station is one side of it, it starts with a W, if it's the other side it starts with a K. I think that if you take WNPG as being from Paisley Park, it should actually start with a K. Dunno what the W and K stand for though.

this:
http://www.oldradio.com/a...trivia.htm
tells you all you ever wanted to know about that subject, and possibly even more than that.

WNPG is a fictional station of course...