Xeogred wrote:Improved music? Was there an updated version of the game only released in Japan or something?
No, the Japanese version of the Master System, (the Sega Mark III) had a unique "FM" chip for sound. Phantasy Star took advantage of this for better audio (I don't know any specific details about all of this, I'm just telling you the the basic idea.

Master Systems from other regions didn't have this chip. No chip, no improved audio.