Oops, got interupted - I'm at work - and didn't include the example I meant to in my post above, about editing to the original story.

Recently, after having heard versions for 30 years, I decided to learn Poor Ellen Smith - nominally a bluegrass song. With the aid of the internet I was able to find that it was a gallows song - written by the accused murderer the night before he hung. Most of the modern bluegrass versions have the guy going to prison and getting out to put flowers on poor Ellen's grave.

The original verses, supposedly written in 1890, were quite long and, to my mind, overly sentimental. They also didn't scan well with the standard bluegrass melody. With a bit of editing I was able to piece together verses that succinctly laid out the plot according to historical record, kept some of the colorful lines, and implied that the guy was going to hang - all in about the same number of verses as the standard bluegrass version.