When I first loaded the web-page, I was expecting it to be something involving stereo or even binaural sound mixing. However, it is in fact only for producing mono sound. The “2d” aspect refers to the rather interesting way in which you mix the sounds.
It is comprised of several sound sources, each producing the sound of a different (synthesized) instrument in a simple music loop. In the middle is a sound receiver, illustrate by concentric circles. You can drag the sound sources closer to or farther from the receiver, affecting how load their are perceived in the final mixed output. (You can hear the results in real-time.) A very nice aspect of the interface is that each source has a circle rotating around it, with a unique colour — the closer a specific source is to the receiver (and hence the louder it will sound), the bigger that circle becomes.
At this stage, you would be forgiven from thinking it’s nothing more than a novel approach to sound mixing. This 2d approach seems to allow you to do nothing more than a 1d mixer system would, since the only relevant dimension effectively seems to be the distance from the receiver to a source. However, the really crafty thing about this is that you can move the receiver too.
This opens up a whole new world of possibilities. You can layout the sources in a particular fashion, and then move the receiver around them to cause the various sources to fade in and out in different configurations. I’m not sure it’s likely to be much use as a pro-audio mixer interface or anything like that (although I could be wrong), but it’s certainly a brilliant idea.
(This is apparently inspired by the AudioPad.)