The three 8 bit version actually all have different music. I know its quite common for Commodore 64 conversions to have a different tune because they were almost always written by a different team altogether. But its unusual for the Spectrum and Amstrad versions to have different music. The only other game I can think of where that had happened before is Dizzy 1 where the Amstrad got an entirely original piece of music written for it and the c64 and spectrum musics were the same compositions if i recall (and only beeper music on the spectrum).
I might have to make a youtube video showing this some time.