As is well known, Burns also made use of other authors' words as well as using others' tunes.

The following occurs in the Herd collection of 1776 (2,206):

Some will court and compliment,
and make a great ado,
some will make of their goodman
and sae will I of you.

John, come kiss me now, now, now,
O John come kiss me now,
John come kiss me by and by
and make nae mair ado.

Burns copied and transformed it to:

O some will court and compliment
and ither some will kiss and daut
but I will mak o' my gudeman
my ain gudeman--it it nae faut

O John, come kiss me now, now, now
O John, my luve, come kiss me now
O John come kiss me by and by
For weel ye ken the way to woo.

O some will court and compliment,
and ither some will prie their mou',
and some will hause in ither's arms,
and that's the way I like to do.

So don't believe those who try to assert that writers never build on other writers' "expression", only on their "ideas". (These are technical terms from copyright jurisprudence). As the example above shows, this would be wrong even if the line between "idea" and "expression" were easy to draw.

T.