Burns only wrote a couple of the verses we sing today and set it to a tune which was older than he was and already popular. It was George Thompson the publisher who set it to the 'Common Tune' after Burns died. Another of Burns'songs 'My Love is Like a Red, Red, Rose' was also set to a different tune to that which we know now (set by R. A. Smith). Burns was a poet and never wrote a tune in his life but his words are what we remember best.