Hi Henni,
it's to do with Yamaha's style format, that makes them so versatile. Basically all one needs to do is change the .sty or .prs extensions to .mid & you got a midifile of the style. Can't do that with any other brand of keyboard style.
I don't know anything about computer programming, but maybe that's helped members like Jorgen & Michael being able to write the utility programs that they do.

I've owned Technics, Roland, Ketron , Yamaha & Korg keyboards over the years, Yamaha is the only one where i've been able to a brand new style into the previous model keyboard. ie psrs700 into psr1500. OK, maybe not perfect, but Jorgens/Michael's programs help to fix problems.
I can't load PA3X style into PA800, can't load PA800 style into PA80.
Strange, I though EMC would have made it possible to convert PA800 to PA80, I've never tried going backwards before just , from one brand to another.

Unfortunately EMC doesn't do a very good job of converting psr to korg, but Donny ( DNJ) mentioned on another post that EMC is converting his Roland & Ketron styles reasonably well to PA500 format. Given me a bizzare idea of maybe converting my PA800 conversions to Roland & then converting to PA50 format. Don't hold much hope that they'll sound any good, but I'm running out of ideas & I figure might be worth a try.