Hi Diane, I am indeed in Japan.
And it's amazing how difficult it is to think of trad songs that would be simple, interesting and useful for lower level students (age 20).
I want songs with vocab/expressions they can USE in future. Baby songs, religious songs, archaic language, doggerel and shanties with lots of shipping terms are not suitable. Repetitive/cumulative songs are great because they get plenty of chance to get comfortable with it. They liked Rattlin' Bog (though they'll never use, or hear, 'rattling' that way) and the 12 days of Christmas. Prickle-eye bush has too much 'stay thy hand' and 'yonder stile' for the moment. Supposing they end up saying 'I've ate goodly meat kind sir' on their holidays! I may have to switch to pop music! (And have you lately noticed how much of that is *rather saucy*!)