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!