Copyright problems with game sounds

[puggsoy]

If what you mean is simply modifying a sound that sounds different, well, I'm not completely sure. One could say that this is the same as using recolours, which are just edited sprites and still aren't really acceptable, however as you're pointing out it isn't as easy to know it's the same sound if you edit it enough. I suppose this might fall under using the sound as an education on how to make your own, but I still think it's not 100% legal if you use it as the basis and simply change it.

Unfortunately I'm not very well versed in legal matters (most of this stuff I've learnt from other people and discussions during my time here) so I can't give you any clear answers. Maybe someone else knows more.