Vocal tuning can transform an average singer into an unbelievable singer. With the aid of modern tools such as autotune and melodyn an audio engineer's job has never been easier. Having said that I'm guessing a million and one takes had to be recorded, before comping them down into the stems used in the final mix. Below you will find two recordings. The first of which is the official release version. The second mix using the live vocal recordings. Rumor has it the engineer was sacked shortly after leaking the dry un-comped stems.