The presence of invisible beings is very strongly believed by the Dyak, and he is persuaded that spirits both good and bad are always round him. As a form of invocation to these spirits, and in all the ceremonial feasts of the Dyaks, as well as on other important occasions, the _pengap_ are sung, sometimes by one man seated on a swing, sometimes by a number of men, who walk up and down the long veranda, dressed in flowing robes, with a long staff in the right hand of each. From what has been said it will be easily understood that there are a great number of different _pengap_ suited to different occasions. In each incantation some special spirit or deity is more specially invoked. At the Dyak Head Feast, Singalang Burong—the Mars of Dyak mythology—is specially invoked to be present in the _pengap_ which is sung. In the feasts connected with farming, Pulang Gana, the god of the soil, is invoked, and asked to drive from their farms all rats and birds and insects that may hurt the paddy. And at the feasts given in honour of the dead all the spirits of dead relatives and friends, as well as those of mythical heroes, are invited to partake of the good things provided. Then, again, when the _manangs_, or Dyak witch-doctors, are called in to cure a sick man, they often walk round and round the sick man, and chant a _pengap_, invoking Salampandai, the Great Spirit-Doctor, to come to their aid, and make their charms efficacious in bringing about the cure of the sick man. Some of the Dyak _pengap_ are of great length, and the singing of them occupies the whole night. The singer or singers begin soon after 8 p.m., and go on till early dawn, only resting for about half an hour, two or three times during the whole night.