Okay, heres the answer to the Olympic opening ceremony.
Almost every single piece of audio that came through your televisions while watching the Olympics was pre-recorded. Every single musical act was mimed.
Arctic Monkeys sounded great, because they recorded there tracks earlier in a studio, where they mimed to there songs and we heard the pre-recorded track, which obviously sounded great.
Paul McCartney was a different story though. Paul McCartney also recorded the tracks in the studio beforehand, but when it came to playing it on the night, he went completely live. Paul had agreed to mime to the television, but would play live to the stadium. So, all of his gear was miked to sound good live, but not to sound good coming through your telly. And Paul did not come in at the same time as his backing track, so they had to shut it off, this leading to a horrible sounding feed of his performance. Drums too loud, piano horrible.. but most of all, his vocal mic sounded atrocious. Everyone knows Paul is losing his voice, but come on that badly? I don't think so. If his vocals were set up properly for a studio or (telly) feed, then he would have sounded much better.
Paul McCartney is a great performer and didn't deserve what happened to him that night. Others would disagree, and say they don't like him... which is fair enough, but you have to admit something went horribly wrong that night.
For people that think Paul has gotten too old and has lost his good voice now, maybe you should look at this which was 6 months AFTER the Olympics -