Matapu is the spirit of the whirled hummer, whose deep roar summons and represents its presence. It is the focus of an important festival that runs for several days, one of the recurring rituals by which the Mehinaku give substance to the invisible spirit-beings and draw them into sociable relation with the village. Like the sacred flutes, the instrument is a body for a spirit rather than a mere object, and its sounding is understood as the being itself made audible.