every 5th song will come from a given playlist.

This kind of defeats the whole idea of shuffling... but you could accomplish this by just making a playlist that contained all of your other playlists and putting your comedy playlist in enough times that the total number of comedy songs equalled 20% of the total number of songs in the playlist.

Sounds like more work than it would be worth, though...

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"