The paper discusses some aspects of a work in progress aimed at the development of technologies for digitization of Bulgarian folk music and building a digital library with Bulgarian folk songs presented with their music, texts and notes. This library provides digital preservation of the sound recordings, lyrics and notations of more than 1000 Bulgarian folk songs and tools for various types of search and analysis of the available resources. The presentation is focused on the subject ontology especially developed for the occasion and its application in the implementation of a tool for semantics oriented search in the lyrics of songs.