A gourd rattle is easy to underestimate because the assembly is so plain. A calabash is dried, cleaned out through a small hole, filled, and fixed onto a wooden handle that usually passes right through the shell. Anyone can make one, and across lowland South America almost everyone does.
The ethnographic literature is insistent, though, that the filling is not ballast. Seeds, small pebbles and, in a number of accounts, fragments of quartz are described as helpers, as concentrated power, or as the crystallised form of something the practitioner has acquired, so that the rattle is understood to contain what it contains even when it is silent. On that reading the instrument is a container first and a sound-maker second, and the sound is evidence of what is inside doing something.
The shell is worked as well as filled. Incised designs, burned patterns and perforations are common, and the perforations in particular are frequently read rather than merely decorative, as eyes, as stars, or as openings. Handles are carved. A rattle that has been in use for years accumulates all of this, which is why an old one is not simply a worn version of a new one.
Handles are worked as carefully as shells. A carved or bound grip fits one person's hand, so an inherited rattle carries the shape of an earlier user in the part nobody photographs.