Unless the music was specifically re-mixed this way, like for 5.1 or something, this is most likely some other phenomina, since that's just not how it works. Live or Studio music is recorded with stereo microphones, and sometimes 'spot' mikes placed to either side of the stage. Low frequencies, whether from an actual instrument, or from your speakers are largely omnidirectional...either to your ears, or to the microphones. While this is a topic for another thread, it has to do with the amplitude and wavelength...both of which tend to be very large at low frequencies.

I'd suspect that what you are hearing has more to do with speaker placement. Take typical door speaker installations, for example. From the drivers seat, the drivers door speaker is nearly 90 degrees off axis. The higher the frequency, the more directional the sound, and the less it will be heard off axis. The passenger side, however, is almost perfectly on axis, so the higher frequencies will seem much louder. At the same time, the passenger speaker is farther away, which affects lower frequencies more, so they will seem softer.

There's actually quite a bit more to this...maybe I just found my next Tech topic...

Toby