Moving away from the population centre of Java, Bali and Madura, we explore the folk music of Sumatra, the Riau Islands, and the Mentawi Islands in the northwest of the country. We start with the people living in the interior uplands of Sumatra, the Toba and the Minangkabau, the latter of which being the largest matrilineal society in the world. The Toba are famed for their intricate Gondang percussion music, whereas the Minangkabau have a form of chamber music that features one or two singers with a single instrument. We move on to the Melayu people inhabiting the Riau islands and the coastal regions of Sumatra, whose language forms the basis of the standard languages of Malaysia and Indonesia - we played some dance music, followed by an Arab-influenced music used in Islamic community rituals such as circumcisions and marriages. We end with the Mentawi islanders off the coast on the other side of Sumatra.