The Pygmies have a complex folk music tradition. Polyphony and counterpoint are common components, as is a varied rhythmic structure. The trumpet-based music of the Bandas has also gained some popularity outside the area due to its jazzy structure. The Ngbaka use an unusual instrument called a mbela, which is made with an arched branch and a string strung between the two ends and held in front of the musician's mouth. When the string is struck, the mouth is used to amplify and modulate the tone. Instruments similar to the mbela are sometimes considered the oldest ancestors of all string instruments [https://web.archive.org/web/20050304011507/http://www.lonelyplanet.com/destinations/africa/central_african_republic/printable.htm].