The Belgian Royal Museum for Central-Africa (RMCA) holds a large collection of ethnographic artifacts, including a sound archive with music recordings from the early 20th Century up to recently. The archive is one of the biggest and best-documented archives worldwide for the region of Central Africa. An on-going digitisation project is part of a strategy to conserve this archive and make it accessible to the public by (i) the digitisation of the data, and (ii) the application of music information retrieval techniques for the digitised data. While state-of-the-art research in music information retrieval aims to search and retrieve music on the basis of content description, most of the existing tools are designed for Western music collections, without any guarantee that these techniques can be applied to music from other cultures. African music, in particular, creates new challenges for content-based description and information retrieval. This paper describes some general problems regarding the content-based description of African and other non-Western music. It suggests an approach for describing pitch structures which will allow for the description of both Western music and non-Western music.