Government support for the arts has been limited to those supporting the ruling political party, so many artists also farm, trade, or use the black market to receive their income. Informal groups of artists provide moral support to artisans to display their art in public. In literature, most Congolese focus on issues of identity, compared to the colonial past. They also focus on topics such as differences between ethnic groups and conflicts between newly adopted and old customs. Some famous authors, poets, and playwrights include Elebe ma Ekonzo, Valerin Mutombo-Diba, Paul Lomami-Tshibamba, Lisembe Elebe, and Mwilambwe Kibawa. The Ingot Cross was introduced by the Portuguese in the late fifteenth century, and is still used as a religious and wealth symbol today. They’re cast from copper, which has inspired a new artistic form in the city of Katanga. Portraits are sketched into a copper sheet, then covered in clay for unique colors and textures. In most large towns and cities, people can buy hand-crafted art. Popular wares are clothing and mats, made from raffia palm tree. Having won their independence 51 years ago, postindependence paintings give a voice to the Congolese. In the performing arts, Kwasa-kwasa, which is a popular dance music, can be heard in most places in DR Congo. It originated in Kinshasa, which is thought to be the African music capital. Popular genres of music are Congo jazz and soukous, or guitar music. Traditional instruments like the piano are used to accompany singers and dancers, when the topic of their piece is about love, gender roles, even political topics. The Mbuti people are known for their vocal style, in which many people sing very different melodies at the same time. In DR Congo, most arts are learned from family members or village elders.