I. Introduction
Music is an important multimedia for modern people because it can alleviate the tense mood. Therefore, people are used to listening to music. In the past few years, it is much easier to access the music due to the advances on Information Technology. For example, the users listen to music through online music websites without downloading the physical music. This incurs a problem for how to retrieve the preferred music from a massive amount of music data. To deal with this problem, a number of previous studies were proposed on music retrieval. Actually, music retrieval can be decomposed into two sub issues, namely system control and search algorithm.