The slit drum must be one of the most ancient musical instruments of human invention. It is also known to have been used as a means of long-distance communication in the ancient cultures of Africa, Asia and the Americas. It has a number of different names, including the log drum, the slit gong and the wood block, but all of the terms refer to essentially the same instrument.

A slit drum is a hollow percussion instrument, usually of bamboo or wood, depending on the materials available. It has one or more slits cut into the surface, which increase the instrument's resonance. Most slit drums have three slits that form an "H" shape. In most cases, the two U-shaped tongues created by the "H" are of different lengths or thicknesses. This means that they produce two different pitches when struck. The closed ends of the slit drum create a resonating chamber, which increases the instrument's volume. A mallet is usually used to strike a slit drum.

Ancient Aztec culture used a type of slit drum called the "teponaztli." It was made of a hardwood log, often one that had been fire-hardened, and it had the usual slits creating an H-shape. These instruments were used in a variety of aspects of Aztec life, including war, long-distance communication, social gatherings and religion. There is even some evidence to support the idea that these drums were used in the infamous human sacrificial rites of the Aztec culture. The blood of the victims was apparently poured into the instruments.

The slit drums of Asia are often made of bamboo, since that plant may be found in abundance on that continent. The "kagul," for example, is a bamboo slit drum of the Maguindanaon people, who live in the Philippines. They use the instrument to scare birds away from food crops as well as to accompany dancing during social gatherings.

In Africa, Southeast Asia and Australia, the slit drum is usually referred to as a slit gong, but the concept of the instrument is exactly the same. A whole long is hollowed out through a narrow slit or slits that run the length of the log. The slits are usually of different length, allowing the players to produce tones of different pitches. Padded sticks are pounded on the log, producing a range of loud musical notes. In Africa, such instruments are used in conjunction with talking drums, which are capable of a much broader range of communication.

The log drum of North America is also a slit drum. It is usually made from cherry or maple wood, and it has the usual dual-pitch capacity resulting from tongues of varying lengths or thicknesses. Prior to the incursion of the Europeans, tribes of this area of the world commonly used such instruments as a means of communication. During the American Revolutionary War, American soldiers adopted this instrument as a method of communicating with other camps.

Finally, the wood block operates on the same principle as that of the slit drum, but usually on a much smaller scale. These instruments are generally small enough to be held in one hand, although the temple wood blocks are often quite large, sometimes so big as to be immovable. Wood blocks are common in the music of East Asia and are generally used for musical rather than communication purposes.