of the indigenous peoples of South Mindanao. From the body of ethnographic and linguistic literature on Mindanao, they are variously known as Tboli, Teboli, Tau Bilil, Tau Bulul or Tagabilil. They term themselves Tboli. Their whereabouts and identity are to some extent confused in the literature; some publications present the Teboli and the Tagabilil as distinct peoples; some locate the Tbolis to the vicinity of the Buluan Lake in the Cotabato Basin or in Agusan del Norte. The Tbolis, then, reside on the mountain slopes on either side of the upper Alah Valley and the coastal area of Maitum, Maasim, and Kiamba. In former times, the Tbolis also inhabited the upper Alah Valley floor. Tigwahonon The Tigwahonon are a subgroup of Manobo originally from the Tigwa River basin near San Fernando, Bukidnon. Umayamnon The Umayamnon are originally from the Umayam River watershed and the headwaters of the Pulangi River. They are a subgroup of the Manobo. Languages The Lumad peoples speak Philippine languages belonging to various branches. These include: Mindanao languages Manobo languages Subanon language South Mindanao languages Mansakan languages Mamanwa language Sangiric languages Musical heritage Most of the Mindanao Lumad groups have a musical heritage consisting of various types of Agung ensembles – ensembles composed of large hanging, suspended or held, bossed/knobbed gongs which act as a drone without any accompanying melodic instrument. Social issues Lumad peoples confront a variety of social issues. Identical with other Indigenous peoples (IPs) across the globe, the IPs in the Philippines represent the country's poorest sector who endure disproportionate access to healthcare, education, and human rights. There are claims that Lumad social issues arise from ethnic grievances that develop into an issue of economic greed. They face loss of ancestral lands due to land grabbing or militarization, economic and social exclusion, and threats to their traditional culture and identity. Lumad groups contend with displacement, extrajudicial killings, harassment of Lumad rights defenders, and forced closure of Lumad schools. Ancestral land rights Lumads face loss of ancestral lands due to land grabbing or militarization. Some communities have been forced out of their lands for resisting encroachment by mining, logging, and energy companies. At the beginning of the 20th century, the Lumad controlled an area that now covers 17 of Mindanao's 24 provinces, but by the 1980 census, they constituted less than 6% of the population of Mindanao and Sulu. Significant migration to Mindanao of Visayans,