When Emma was new born and colicky, I spent hours and hours singing every song I could think of to try to pacify her. Eventually, hoarse from days of this, I stumbled upon 'Iron Man' by Black Sabbath, a song that dates to the era in which I myself was born.
She shut up and listened immediately. So it's become one of the songs I've sung her ever since. Today I got a text message from Mari saying, "Emma hummed herself a lullaby as she was falling asleep. Guess which song it was."
Yes, I've attained the secret bonus level of fatherhood; teaching your infant daughter to sing Iron Man at a year and a half.