Continuing with what Joe started:

I've noticed that the songwriters themselves can be among the worst when it comes to changing their own lyrics when the mood suits them.

When trying to put together the "corrrect" lyrics for a few Woody Guthrie songs I found that there were many variations in what he sang or wrote down. Anyone who has researched "Tom Joad" knows what I mean.

And Eric Bogle comes to mind, as well. All the versions I heard years ago of "And the Band Played Waltzing Matilda" vary greatly with the lyrics posted on his website. Bogle freely admits to revising the lyrics to many of his songs.

Makes it really hard to know what the "authentic" version of a song is, in some cases.

Jay