Do you need an artists permission to use their instrumental and release the song on itunes?

I am a rapper and I have many different songs recorded over other rappers beats..I am not too familiar with the legality of everything so I was wondering, if I just release the songs with their beats on itunes and give credit to the artists and their record companies for the beats would that suffice? Or would i need to obtain permission from each individual artist to release the songs on itunes?