These three costumed men are playing Gnawa music. This genre of African Islamic songs originated in West and Central Africa as part of a healing ritual. The large, iron, castanet-like instruments are called krakebs. Similar to all entertainers at Jemaa el Fna, they expect to receive pocket change after their performance. The Moroccan dirham is equivalent to about a quarter in U.S. currency. You should be aware it is illegal to remove dirhams from the country. So make sure to exchange them at your hotel or the airport before leaving. Or if you are careless, a pickpocket will be happy to take your money at Jemaa el Fna.