Rollenspiele » Strange sound problem while playing super mario rpg

Hello,

first two levels sound was ok and nothing happened but when i got to mushroom kingdom this strange problem started.
Problem is that the music and sound went from completely perfect to horribly scratchy. Don't know if it continues after the mushroom kingdom but still if it continues then it will bother me alot. Is this normal? First i thought maybe i have so shitty computer that it just doesn't run snes games that well because i haven't updated my computer since 2005 but when i turned fps on it showed 60/60.
Please help

I didn't find the right solution from the internet.

References:
http://www.snes9x.com/phpbb3/viewtopic.php?f=6&t=4786
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Thanks