If you sing any song softly and sweetly, it works. My husband sang our son the fight song from his school, calmly and crooningly, and it worked fine.
My fab is Brahms lullaby.
I always make my own too.... Lol ;)
My kids loved itsy bitsy spider, im a little teapot. We bought the books and they had lot if verses that I would sing along with the book. My little girl loves the nursery rhyme "sing a song of six pence" and laughs at the end when up say "up came a black bird and snipped off her nose!" I guess she's a mean little thing like me! Lol hubby doesn't know many songs so he sings the alphabet over and over. I guess its all about the tone u sing them in.