Originally posted by bruno123:
Look at The Christmas Song, there are many chords which do not relate to the key the music was written.
The Christmas song begins and ends in the same key, with a few very tasty key changes in the middle. The simple truth is - the key IS established at the beginning of that particular song. It's also true that sometimes the first chord is NOT the key, but when that happens, USUALLY, the last chord is !

I love unusual key changes in the bridge ... try All the things you are sometime ! Fun changes !