The listener is surrounded by musical parts and vocal harmonies. The same music that you've been listening to for all these years is reborn and sounds fresh again. Mixing a surround project is actually easier than trying to mix the same project in just two speakers. There's so much more room to place the individual tracks. Engineers are experimenting with this newfound sense of freedom and no one is really sure how to approach the world of 5.1-channel surround.
Fundamental questions loom regarding the philosophy of recording and mixing.
Reality went out the door when Les Paul started using overdubs in his early 3-track recordings. Maybe there are several valid ways to mix a multi channel project. During the mixing of the Brahms Piano Quintet in F Minor , I was heartened to find that the musicians enthusiastically endorsed the aggressive placement of the instruments around the room. The listener hears the individual parts from the middle of the ensemble and can adjust his or her own blend by moving closer to the instruments that need to be louder. Admittedly, the experience is completely unlike attending a concert, but it is nonetheless compelling and engaging.