At a dance a few weeks ago I suggested we try Winster Gallop in a minor key, starting off as a major and then for the repeat going minor. It is not just a question of trying to play minor chords over the existing melody because the melody has to be subtly changed too. Winster Gallop is a great tune for dancing but I hate playing it and turning it into a minor key transformed it. Before anyone says "No you can't do that!", that is exactly what happened in the tradition and one of many reasons why there are so many variants of songs and tunes.