I sing the Titanic and, at a recent sing-around, one person commented that the jolly tune / tragic story mismatch was very powerful; it made her far more aware of the tragedy than a sad, minor tune would have done.

Prior to her saying that I had always felt a tiny bit uncomfortable about singing it in case anyone thought it was callous but now I don't - she's right, it really does draw your attention to the horror of it.