A NEW MUSIC-INSPIRED HARMONY BASED OPTIMIZATION ALGORITHM. THEORY AND APPLICATIONS. I. Kougias 1 and N. Theodosiou 2 Division of Hydraulics and Environmental Engineering Department of Civil Engineering Aristotle University of Thessaloniki 541 24 Thessaloniki, Greece E-mail: ikougias@civil.auth.gr 1 , niktheod@civil.auth.gr 2 ABSTRACT During the past decades the state-of-the-art, as far as optimization techniques are concerned, is focused on algorithms inspired by physical phenomena, such as the genetic algorithms, due to their ability to solve complex optimization problems and overcoming the limitations of numerical programming methods, especially when dealing with problems involving several local optima. In this paper a novel, powerful optimization tool is outlined; namely the music-inspired harmony based optimization algorithm. The algorithm is based on the observation that the aim of music creation is the quest of the perfect state of harmony. Such a quest is relevant to the optimization procedures which also seek the “perfect” solution. Since the year 2000, when the algorithm was first presented, a series of interesting articles were published concerning the application of the certain algorithm in solving a vast variety of problems, from sudoku puzzles to space applications. The paper at hand presents the development of HSA, as well as the early findings. The progress made so far indicates the acceptance of the method by the scientists involved in optimization simulation. After extensive research in several scientific databases, the growth of HSA literature is presented. Furthermore, the authors who formulated the allocation of HSA applications among diverse scientific fields, demonstrate the effectiveness and robustness of the HS algorithm. The steps of this innovative algorithm are presented in detail, along with the theory on which HSA is based. Finally, HSA’s possibilities for further development are investigated. 1