In a series of projects, I have worked on the description and documentation of Tabaq (a Kordofan Nubian language) and Katla (a Niger-Congo language) of Sudan. Tabaq was originally spoken in the north-western Nuba Mountains, but many Tabaq have now left this area and have migrated to various urban centers of North Sudan. There are currently about 1800 people who consider themselves Tabaq and who speak this language to varying degrees of fluency. In close cooperation between the University of Cologne (Birgit Hellwig, Gertrud Schneider-Blum) and the University of Khartoum (Abdelrahim Mugaddam, Khaleel Bakheet Khaleel, Khalifa Jabr Eldar), we conducted a sociolinguistic survey on language use and attitudes, and created an annotated corpus of various genres. The Tabaq survey and corpus complement our own earlier research on the neighboring non-related Niger-Congo languages Tima (Schneider-Blum, since 2006) and Katla (Hellwig, 2006-2008). The three parallel corpora now allow us to investigate convergences and differences among the languages, and to place our findings in a historical and sociolinguistic context, and they continue to inform our present-day research. The projects were funded through a Postdoctoral Fellowship from La Trobe University, Melbourne, and a Major Documentation Grant from the Endangered Languages Documentation Programme.