Kutubu drums (sapo) are of two types: one is the familiar 'fish-mouth' (though the 'mouth' is called sapo-kesa, 'drum-treefork'); the other might be called the 'goblet' type.

The drum is about 2 ft 6 ins [75cm] long, and without a handle. It is slenderly made and when not in use is carefully wrapped in bark-cloth and hung up. It is evidently a valued possession and I did not succeed in buying one. It has already been mentioned that drums are never used except in connection with the 'Usane' cult which deals with the curing of certain sicknesses. It is only as a culmination to a long course of treatment that a village holds an 'usanehabu', i.e. feast accompanied by a dance with drums. It is said that this cult has found its way to Kutubu from the Mubi via Fimaga, Foi, Segaro and Turigi. I do not know where the last two places would appear on the map, but they are seemingly away to the south-east. Some informants volunteered the opinion that the drums (of both kinds) had been introduced to Kutubu with the cult.

Excerpt from FE Williams, 'Natives of Lake Kutubu, Papua', Oceania, vol 11 no 2, Dec 1940, pg. 149