i dont think it's that strange. i just relaxed for 15 minutes with some quiet music playing and felt the same effect.
as for it being related to astral projection, i would hardly believe it no matter what you said. the heart is the strongest muscle in the body. when i relax with music i almost stop moving, though some movement is likely. my heart pumps 5 liters of blood per minute [ http://www.smm.org/heart/lessons/lesson2.htm ] so it really wouldnt surprise me if what you're feeling is the movement of your heart and the changes in pressure within the blood vessels
^my brain at work
