Sometimes "murdering" a song can be as much about changing it as it is about doing a really bad rendition. In the case of Cohens Hallelujah, you may have seen the video of the little school girl in Ireland (?) who redid it as a Christian song. It went virile. The backlash was the fear that the latest version might eclipse the original. Other times an artist can breath life into a song that was badly needed. Arlo Guthrie put Steve Goodman on the map with the remake of "City of New Orleans". Steve Goodman was grateful for that.