A rather unrelated case in point.
The Brand New Monty Python Bok, published sometime in the early 1970's, contained lots of wonderful material. It's one of those books that not only make you laugh outloud while reading, but which you also want to "read" to someone else. It's not the first place you'd look for an examination of the question of versions, but seek and ye shall find.
The book contains a number of "famous first drafts" by well known poets - versions that suggest that the creative process always passes through homage (at the least) to someone else.

I use some of these rather extreme examples of borrowing as a starting point for creativity in another project of mine. In the example above T.S. Eliot takes off from his Love Song of J. Alfred Prufrock in order to sing a rather different sort of love song, a love song that according to the Historic American Sheet Music site, affiliated with Duke University, was written by a rather prolific popular song writer, Geoffrey O'Hara.
Go to: The tip of the iceberg, or
Go to: Reflections of a Spring Cleaner.