A chacapa is about as simple as a ritual instrument gets. Leaves are gathered, dried, and bound at their stems into a bunch or a flat fan that fits one hand. There is no resonator, no membrane and no shell. Shaken, it makes a dry rushing sound, closer to rain on a roof or to wind through undergrowth than to the sharp report of a gourd rattle, and it can be played very quietly or worked up into something continuous and enveloping.
The leaves most often named for it belong to grasses of the genus Pariana, though what is used depends on what grows nearby. The bundle is made rather than bought, costs nothing but the gathering, and wears out with use, which means a chacapa is a consumable rather than an heirloom. That is a different relationship from the one a practitioner has with a drum or a costume, and it shows in how the object is treated.
In use the rattle is not held still. It is moved: over a person, around them, close to the head, along the length of the body, so that the sound arrives from changing directions. Practitioners describe the sound as the thing that acts, which makes the instrument closer to a tool than to an accompaniment.
Because the bundle is soft it can be brought right up against a body without harm, which a gourd rattle cannot, and much of its use is at very close range.