that will gradually "mute" the end of a song that is playing and start the next song in the play list before the old song fully ended, so there is no gap between songs played. Any ideas?
What version of Windows Media Player are you using?
... I ask because what you describe is called 'crossfade' and has been a standard feature in that program for a number of years now (versions 10 and newer definitely have it... not sure about 9 and older). If you have the same version I'm running, the View >> Enhancements toolbar. Should help you out greatly.
No prob. Totally understandable. Glad I could help.
On a similar topic, that's one of the biggest issues I have with Real Player's free software... it still doesn't come with a few basic features like crossfade.