Don't feel bad about not knowing about the triangle thing. It confused me a bit too until another owner told me how it worked (and I have a degree in Computer Science)! I didn't spot that the icon was something I could interact with at first. I had fluked it once though and it was set on my "everything" list, so I was happy for a while. D'oh!

A couple of nice features also to do with that little play icon:

First: If you hold the "down" button on it for a second or so, you'll get options to insert/append etc. So, you can have a nice long playlist running and think to yourself "I'd really like to hear album X right now", and insert it such that it resumes your long playlist in the same place after the album is finished. Or you could queue several albums up to play one after the other with "append".

Second: The play icon plays all songs AND sub-playlists at the current level. So, if you set up a folder for each artist with their albums as sub-playlists (best done with jEmplode and a soup playlist) you can choose to play just "Dark Side of the Moon", or "Pink Floyd" which would include all of their albums on the Empeg.