Just my two penn'orth,

I think that the first test to be applied is "Does the version/variation make sense?" For example:- In the "Queen" song "Bohemian Rhapsody" I have HEARD someone sing "..Beealzebub has a devil for a sideboard..." Obvious rubbish and therefore either misheard or someone trying to be silly, however, in "No Man's Land" is the chorus
"...Did the bugle PLAY the Last Post in chorus.."
or
"...Did the bugle SING the Last Post in chorus.." ?
Only a minor variation, I admit. By the same token, In the song "Gallipoli" I tend to sing<1>
"...They dressed me in khaki, they gave me a gun..."
instead of
"... They gave me a tin hat, they gave me a gun..."
just from a point of historical accuracy (steel helmets were never used in the Dardenelles campaign).
In both cases the variation from the original make sense and COULD (were these "oral tradition" songs) have formed new versions while the first example would be forever wrong.

Does this make sense to anyone?

Walrus

<1> I should point out that I sing purely for my own pleasure, (with a voice like mine there's no pleasure for anyone listening).