While some were simple utilitarian pieces they could also be highly elaborate works of sculpture while still retaining their function. Variations in the thickness of the walls would vary the tones when struck by heavy wooden drum sticks. Slit-log drums are common in the drum communication systems of Papua New Guinea, where they are known in Tok Pisin as garamut. Message drums, or more properly slit gongs, with hollow chambers and long, narrow openings that resonate when struck, are larger all-wood instruments hollowed out from a single log. In the 20th century the talking drums have become a part of popular music in West Africa, especially in the music genres of Jùjú (Nigeria) and Mbalax (Senegal).