you are remixing someone elses song and putting it up, or is it a new recording?
If it's just a remix there could be copyright issues...but, nothing is gonna happen if you just put it up. They arent gonna slap you in jail or give you a fine or anything...they would first just ask you to take it down.
I say just go for it. If someone is upset, they tell you and you take it down and all is good again. Otherwise, all is good
