[paul.fr]

when i have my earphones on, i have noticed that when i sway my head from side to side, apart from looking mad, that the music seems fluid. It's as if the music is flowing in the direction of my head movements...slowly going side to side across my head.

why would that be?

[lyner]

Could it be that your balance organs are telling you to expect the sound to be changing? It normally would change in phase as you move about and your balance sensors may provide an input which will explain / compensate what your brain 'hears'. The fact that it doesn't could be confusing this process. You are providing some feedback to correct for something which isn't there.
Howzat  for an idea?

[JimBob]

How is "water on the brain" for and idea?

[neilep]

I don't wish to partake in any discussion involving audio whilst my left ear  is being so non-participatory in aural dissemination !