The discussion needs to be clear what copywrite is. It is legal protection to prevent anyone from using or altering or claiming authorship your work without your permission to do it whether that be commercially or for no monetary gain. It has nothing to do with what effort or money or creativity was put in to creat the work.

The simple question is :

Has the work been registered under copywrite ?

If it has thenthe copywrite laws apply. If it hasnt then anyone can use it at will without any fear of the law.

So if yamaha's or korgs or whoever have not copywrited the sounds from their instruments ( i dont even know if this is practically possible) then its all fair game.