There ain't nothing wrong with those lines from The Rising of the Moon - they work very well in my opinion. My point was that the addition of the word "soon" was unneccessary and redundant from the point of view of adding any meaning to the sentence . Make ready as quickly as possible would have been 'correct', but quick and soon and helps the rhymne and sounds better which is what is important when it comes to a song .
The double negative works in a similar way to strenghens an idea - as in "ain't no use". The double negative was once widely used in everyday speech to emphasise a negative .It was discredited and done away with by formal grammarians some time around the nineteenth century so as to make language conform to the formal rules of mathematics where a double negative equals a positive .