A slit drum or slit gong is a hollow percussion instrument. In spite of its often being called a drum, it is not a true drum because it lacks a drumhead, the membrane stretched across the top of a true drum). It is classed instead as an idiophone in which the entire instrument vibrates, usually carved or constructed from bamboo or wood, in the form of a mostly closed hollow chamber with one or more slits in it. It is played by striking near the edge of the slit. In some designs, the slit is a single straight line; in others, the slit is used to create one or more "tongues", achieved by cutting three sides of a rectangular (or similar) shape and leaving the fourth side attached. Most slit drums have one slit, though two and three slits (often resembling an "H" and thereby forming two tongues) occur. Tongues of different areas or thicknesses will produce different pitches. Slit drums are used throughout Africa, Southeast Asia, and Oceania. In Africa such drums, strategically situated for optimal acoustic transmission (e.g., along a river or valley), have been used for long-distance communication.
The ends of a slit drum are closed so that the shell becomes the resonating chamber for the sound vibrations created when the tongues are struck, usually with a stick or mallet. The resonating chamber increases the volume of the sound produced by the tongue and presents the sound through an open port. If the resonating chamber is the correct size for the pitch being produced by the tongue, which means it has the correct volume of airspace to complete one full sound wave for that particular pitch, the instrument will be more efficient and louder.
The people of Vanuatu cut a large log with "totem" type carvings on the outer surface and hollow out the center leaving only a slit down the front. This hollowed out log gives the deep resonance of drums when hit on the outside with sticks.
The wooden fish works like a slit drum but is rarely classified with the other slit drums.