According to Jim's CD, each file must have a specific name for the board to recognize it, with the proper suffix ending as well. I don't have my literature anymore as I had to sell my board or else I would give you specifics.
There is only space for one hum. For each clash, there is a specific "nomenclature" that has to be used. You can also program the board for random, or to have each clash played in a specific order.