Out of phase. If you had a speaker bridged across your stereo amp, or some other way of listening to the out of phase component of the signal the effect would be more dramatic. This is matrix multichannel.
How did they do that?
I was listening to the new Annie Lenox CD, "Bare", when cut #3, 'The Hurting Time' came up - all of a sudden, I'm hearing the music behind me - with my 2ch system. I actually turned around wondering if someone installed speakers in the back of my room w/o telling me. This phenomena only existed at the beginning of this one song on the. Any ideas? An inquiring mind needs to know. Thanks!