In the harmony search (HS) method, there are only three distinguishing factors: harmony memory considering rate (HMCR), pitch adjusting rate (PAR), and HS memory (HM), used to control the quality of solutions and balance the intensification and diversification during the search process. These three operators determine the attractive properties of the HS including structure simplicity and fast convergence, which also promote the research of improved HS algorithms and fusion strategies with other nature-inspired computational (NIC) approaches. However, the consideration of balance intensification and diversification is inevitably a challenging problem in the hybrid NIC algorithms that possesses the advantages of robustness, efficiency, and accuracy, and these objectives usually conflict each other. Additionally, the ‘no free lunch (NFL)’ theorem should also be taken into account when handling various optimization problems in engineering. This chapter gives a concise summary of the book and points out the further research trend of the HS method.