In traditional content-based music information retrieval systems, users may face with longer response time, since the traditional systems mostly do syntactic processing to match query melody and whole melodies of the underlying music database. Hence, there has been a growing need for theme melody index that can support to quick retrieve the relevant music to user’s query melody. In this paper, we suggested an automatic mechanism for constructing the theme melody index from large music database and also showed how the theme melody index can be used for content-based music retrievals by implementing a prototype system.