Classic roots reggae from John Holt, his nursery rhyme take on Ali Baba & co.:
(According to the great site jamrid.com it's from 1970 - check link below the videos for a list of songs which use this riddim, the Ali Baba Riddim!)...
Ali Baba Riddim Dub w. John Holt, King Tubby & Augustus Pablo
Arabian Dub on the Ali Baba Riddim
Info on "Ali Baba" from jamrid: