Dude, sometimes, if you change a note, or a word or anything for that matter from a masterpiece, you just ruin it. Most Mozart's pieces are like that, and I think that it's totally true for anything by Bach. Now it's also true for the beatles...
Create something that cannot be improved or perfected, and you'll see what I mean (By the way, they only had four tracks back then, so try to create what they did, it sounded like a ufo back then)