As someone who is a late entrant to this discussion there is an interesting parallel with the idea that we all alter/adapt songs for our own use - adding/subtracting a little or changing words here or there . On the Musical Traditions website Rod Stradling has started putting togethere a record of how people have changed songs, and why. Makes interesting reading

http://www.mustrad.org.uk/songbook/s_index.htm

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