cushman, thanks for the great explanation. So, is the tweak recursive? If I'm listening to REM and press "Artist", does it go through the entire running order and swap each REM song it finds, one after another, to be immediately after the one I'm listening to? So, even if it's on Shuffle, will it stack the shuffled REM songs all back to back, and pick up with the rest of the shuffled playlist after that?

So, what is the proper use for that? Say I'm listening to my shuffle playlist, and I get to an REM song, so I press "Artist", and it then stacks my 9 REM albums back to back in shuffled order after the song I'm listening to. So, after I hear 6 REM songs, I want to go back to the random order (ensuring that I don't re-hear the songs I've already listened to). How is this possible? Or how can I skip to another artist in the group without skipping forward through 9 albums worth of REM tracks?

Tweaking makes me think that mood playlists could be implemented by genre tag quite nicely. Listening to a random playlist and a song that fits the mood comes on, so press Genre and have it grab all the tracks for that mood. But the above question is still looming; how do I get back to normal shuffle (or whatever sort order) mode; how do I undo the tweak?

Thanks again. Now my mind is reeling with a nested inheritance hierarchy for mood playlists, using "exclude as child" or whatever to give me more granular control over higher levels fo the hierarchy... or something.