1. Introduction -- 2. Overview of emotion description and recognition -- 3. Music features -- 4. Dimensional MER by regression -- 5. Ranking-based emotion annotation and model training -- 6. Fuzzy classification of music emotion -- 7. Personalized MER and groupwise MER -- 8. Two-layer personalization -- 9. Probability music emotion distribution prediction -- 10. Lyrics analysis and its application to MER -- 11. Chord recognition and its application to MER -- 12. Gene classification and its application to MER -- 13. Music retrieval in the emotion plane -- 14. Future research directions.