Chord is one of the most important mid-level features of music. With chord sequence, songs that are similar in various aspects can be identified and retrieved more effectively. This chapter describes the extraction of chord features from the chord sequence of music pieces to improve MER. We begin with the introduction of a chord recognition system for recognizing the chord sequence from low-level music features and then describe two features that are computed from the chord sequence. Empirical evaluation shows that these chord features improve the accuracy of valence classification.