Song translation is a difficult art. Not only does the translator have to cope with rhyme patter, alliteration, metre, etc., but he/she also has to convey the meaning of the song and the allusions within it. Unless, of course, the song tune is just a vehicle for something completely different. All that's understood.

But my caveat is with the different directions that the translations often take, losing the point of the original. Johnny Mercer's words for "Autumn Leaves" are no match for "Les Feuilles Mortes" of Jacques Prévert - and Dorcas Cochran completely glosses over the point of Jean Rodor's "Sous Les Ponts De Paris" to turn it into a sickly romantic offering.