i think you've entered a mine field here, it does say original songs only on myspace, which basically means it's a disclaimer so myspace cant be taken to court for what you put up, if you understand me?
there are hundreds of songs eg whisky in the jar, by thin lizzie, that are credited original/arrangement by...! but i dont know if that would work while the copyright is still active, please dont do a george harrison [my sweet lord] and end up having to pay millions for what could be someone else's song. you might try yahoo answers... they get similar queries there.
hope this helps
phill