The Music Archive of the Ethnological Museum (National Museums Berlin, Germany) houses a large number of recordings on phonograph cylinders and magnetic tapes. The project ILKAR (Integrated Solutions for Preservation, Archiving and Conservation of Endangered Magnetic Tapes and Cylinders) aims at prioritising the digitisation of the more than 10,000 magnetic tapes of the Archive. In this contribution, the usefulness of Attenuated Total Reflectance - Fourier Transform Infrared Spectroscopy for the characterisation of the constituent materials of magnetic tapes is discussed. The final aim of the research is the characterisation of the most endangered materials of the Archive's collection and the evaluation of their conservation state. A range of complementary techniques should aid in the characterisation of the main tape types housed in the archive and will help to achieve a better understanding of their decay processes.