"Nobody's going to be impressed when you explain that you're playing the tune they way you heard it growing up in Brooklyn." But maybe you leant it growing up in Brooklyn from your grandmother who grew uop in some place with more cred in the old-timey world?

And if anyionbe doesn't have the time to take up that link to the Fields of Athenry, to cut to the chase, it sesm pretty certain that Pete St John did write it, and that the alleged original from back in the 1880s didn't actually exist until some time after he wrote it. Only rumours like that have a tendency to spring up like weeds.

I'd call any variation a variant or a version myself. Some start as mistakes, some are conscious alterations to help a singer feel right singing the song. Even the simple mistakes are bringing out the potential variants that a song has, lyrically or musically.

Oh yes - I've always heard it and sung it as "Did the band play the last post in chorus". Though come to think of it, it's bugles that play it - but band scans more easily. (I've just checked with the Ossian "Songs & Ballads popular in Ireland", and it's got "the band played the Last Post and chorus" - that's four variants on that one line. Not bad.)