My father played his guitar and sang a very politically incorrect drinking song to my brothers and me as a lullaby. It begins (and you have to imagine this sung in a soft, loving tone) "Oh, the night that Paddy Murphy died, I never will forget. We all got stinkin' drunk that night and some ain't sober yet" -- and it gets worse from there! But Daddy's soothing voice sent us off to dreamland every time.
I sang the same song to my children when they were babies, at least until they started to understand the words. That taught me that the song itself isn't what's important -- it's the love in the parent's voice that matters. It still makes me laugh to think that's how we were lulled to sleep!