Sorry about the delay once again. I have simply been too exhausted to sit down at the computer without falling asleep.
I have been thinking about the implications of the "up" vector you mentioned, but I haven't figured it out completely yet.
Let's try with some illustrations. First, to avoid confusion, here are 3 pictures of the listener:
A top-down view of the listener
The listener seen from the back
In the next image, imagine that the purple background is the 2d plane of the game world:
This is the default mode of SFML. It makes perfect sense and is easy to understand.
The red arrows represent the way I would like to rotate the listener, which isn't possible.
The following picture represents your first suggestion for what I could do instead:
The problem with this is that some sounds will end up behind the listener, which is not desired.
So... That brings us up to now. Your new suggestion is that I translate x/y coordinates of the 2D game world to the x/z coordinates of the listener's 3D world. But I don't see how that changes anything. I still can't rotate the listener to follow the view. I can make him look in different directions, but I can't mare him stand on his head, no matter which way is defined as "up".