Steel tongue drum
A steel tongue drum, tank drum, or hank drum is a round steel slit/tongue drum in the Idiophone family originally fashioned from a propane cylinder. Description. A steel tongue drum can be made from an empty (often 20lb) propane tank. The tank is flipped over, the base cut/knocked off; and seven to ten tongues are cut radially into the bottom of the tank, forming the top of the instrument. Steel tongue drum can also be made from new unused tank heads. The tongues can be tuned by the maker by varying the length of  the cuts, or by adding weights, often neodymium magnets to the tongues. The steel tongue drum is often tuned to pentatonic scales but can be tuned to the diatonic scale, the chromatic scale, or any set of notes the maker chooses. The instrument is played with the fingers or with mallets. It boasts a pleasant, bell-like tone. History. The steel tongue drum is based on the wooden slit drum. The slit drum is known to have been developed independently by multiple ancient civilizations including Africans, Aztecs, and Indonesians. They were used for both ritual and entertainment in these ancient  civilizations. The steel tongue drum today had several predecessors, most notably the Whale Drum in 1990 by Jim Doble and the Tambiro by Felle Vega. In February 2007 Dennis Havlena, inspired by the physical properties of the Tambiro and the tone layout of the Hang, created a steel tongue drum with a circular cross pattern layout from an empty 20-pound propane tank. The name 'Hank Drum' came from a combination of "Hang" and "tank". Dennis Havlena's instrument, in turn, has inspired other steel tongue drum inventions. Today there are a lot of vendors of commercial versions of the  steel tongue drum worldwide. Construction. Slit drums were originally built out of hollowed out logs or bamboo, but the steel tank drum is made from steel and often built from 20 gallon propane tanks. The construction is usually enclosed, unlike other open-bottom drums, so the sound produced resonates through the steel and vibrating air escaped from the slits. When built from a steel propane tank, the paint is usually ground off and properly sized slits are cut and tuned by means of filing or adding material through soldering or welding.