1. An apparatus, comprising: a calculation unit to calculate respective scores between a plurality of audio files and a query; a dynamic clustering unit to identify first audio files, of the plurality of audio files, based on the calculated respective scores between the plurality of audio files and the query, and to cluster the identified first audio files by calculating scores between the identified first audio files; a static clustering unit to identify second audio files, of the plurality of audio files, based on the calculated respective scores between the plurality of audio files and the query, and to cluster the identifyied second audio files based on respective weights of core index words of the identified second audio files, wherein the weights of the core index words are respective weights of extracted core index words for the plurality of audio files; and an output to output a result of dynamic clustering of the identified first audio files and/or a result of static clustering of the identified second audio files.