THE YIN YANG THEORY IN SOUND AND MUSIC: A FIRST EXPLORATION Leonardo Gabrielli Dept. Information Engineering, Universit` a Politecnica delle Marche, Ancona, Italy l.gabrielli@univpm.it Daniele Gabrielli Universit` a di Macerata, Macerata, Italy ABSTRACT Today the Chinese theory of the Yin and Yang principles is well known in western countries, often in its philosophical aspects. However, in the far east it has been used for mil- lenia to explain and solve pragmatic problems. Notwith- standing its fuzzy and holistic nature, the Yin Yang theory has already been successfully applied to the analysis of physical and biological systems. In this paper, the the- ory is extended to the field of acoustic signals and their time-frequency representation, allowing for a simple yet functional way to analyze, discuss and formalize various aspects of sound, accessible to experts and non-experts. The framework can also have application on synthesis al- gorithms, generative music and music therapy. Two high- level features for automatic analysis are proposed based on MPEG-7 low-level descriptors and future scenarios to assess sound properties and their effect on human subjects are discussed. 1. INTRODUCTION For millennia, the Yin Yang theory has been one of the pil- lars of ancient Asian thoughts, used practically to describe all aspects of life and properties of objects and living be- ings. The theory is the pillar of several eastern philoso- phies and beliefs, such as Taoism and Zen. The Bagua (eight trigrams) and Five Element theory, on which Feng Shui and I King are based, stem from Yin and Yang. Western thinkers have been highly fascinated by such eastern concepts. A remarkable example in contemporary music is John Cage’s extensive use of the I King divina- tion book for composition by chance [12]. It must be noted, however, that the Yin Yang theory must not be re- garded “as a religious belief or a principle of lifestyle“ [18] but a rather more practical knowledge. Not surpris- ingly some western scientists have found connections be- tween the Chinese theory and the results of contemporary physics. An extensive review of the funding principle to ancient eastern theories and the evidences of their validity in modern physics is contained in F. Capra’s work “The Tao of Physics” [3]. Holistic thinking is also highly re- garded in contemporary theory of dynamical systems or chaos theory, which exploits new theories drawn from bi- ology and mathematics [4]. Although the seemingly dualist approach at the basis of this theory may seem excessively reductionist, thus ap- parently making the object of highly specialized techni- cal knowledge a trivial matter, it is not. On the contrary, by incorporating many aspects of the object under anal- ysis, it achieves a holistic gaze, enabling to better deal with complex phenomena such as those related to human perception, emotion and health. Objections to holistic ap- proaches are often made by scientists, especially in fields like medicine and medical care where the health of people is at stake. It must be stated, however, that modern medi- cal science because of the drastically sectorial knowledge (which helped fighting e.g. communicable diseases in the past century), is now failing to provide effective therapies and prevention to noncommunicable diseases such as car- diovascular diseases, cancers, chronic respiratory diseases and diabetes [2], which are found in both high-income and low-income countries and can be prevented with a change in lifestyle and dietary habits [31]. In fact, there have been documented cases of successful applications of holistic approaches to medicine. An excellent example is the mac- robiotic diet [24, 20, 17], a well-defined dietary regimen based on the Yin Yang principle and on the Five Elements theory, which is proving capable of reducing risks and greatly improve health conditions in individuals affected by several chronic diseases [25, 13, 11]. The Yin Yang theory has also been applied in com- putational sciences and logic, where it inspired the for- malization of a bipolar fuzzy set [35], machine learning techniques [34, 33, 16] and of a pattern classification sys- tem for mental disorders [36]. We can probably say that the ancient Yin Yang theory can be applied to most, if not all, fields of human knowledge and practice, with good chances of achieving benefits by gathering a broader un- derstanding. It is our belief, thus, that the Yin Yang theory can be applied to music and sound by direct extension of the physical properties of Yin and Yang, as has been done in other fields of physics and biology. Henceforth, if this theory is properly applied and it is correlated to emotional states and human activities (the ancient theory does cate- gorize these in terms of Yin and Yang), it can prove prof- itable for different scenarios, e.g.: • for composers or performers to drive high-level au- tomatic composition or synthesis techniques in a