Song in the opening credits?

Ok... so I know a lot of people have been searching for songs from this film unsuccessfully but I was wondering if anyone new what the song in the opening credits was or where I could find it. The lyrics go "hush my child, baby don't you cry, mamas here to help you by and by" or something along those lines and there's a harmonica being played though out. Any help you can give me would be very much appreciated!