Rhythm Zoo: Music Composition Modeled on Genetic Networks Anna Lindemann 1 and Eric Lindemann 2 1 University of Connecticut, USA, Email: aklindemann@gmail.com 2 Synful, USA, Email: eric@synful.com Abstract Inspired by the cyclical patterns of gene expression found in de- veloping organisms, and the resonance these patterns have with rhythmic and harmonic cycles in music, our ongoing creative work focuses on the use of hierarchical Random Boolean Net- works (RBNs) for musical creation. RBN models are widely used in scientific research to study the genetic networks underlying biological systems. A hierarchical RBN consists of multiple, in- terconnected sub-networks that run at different time scales. As a result, the sub-networks disrupt and influence each other’s cycli- cal behaviors. In biology, these patterns of interference, which manifest in genetic networks, are what define biological structure: for instance, which part of an organism will become a head versus a tail. Inspired by the way that disruption creates biological struc- ture, we use hierarchical systems of musical RBNs to create mu- sical form and compose “musical organisms.” Keywords Music, Biology, Random Boolean Network (RBN), Generative Art, Genetic Networks A Case for Biological Art Life on earth is filled with beauty, diversity, complexity, and even absurdity—many of the qualities artists often strive to capture in creative work. We believe that artists can learn from the billions of years that life on earth has had for creative exploration by taking inspiration from the processes that develop these qualities in living organisms. DNA acts as the code for biological development and has been a source of inspiration for the development of a wide range of artworks, including music. Susumu Ohno and Midori Ohno’s 1986 paper “The all pervasive principle of repetitious recurrence governs not only coding sequence construction but also human endeavor in musical composi- tion” compares repetitions found in DNA sequences with the repetitions found in music, and suggests the possibility for creating music based on DNA as well as DNA based on music [1]. Other composers, musicians, and musician- biologist collaboratives have developed a variety of ap- proaches to creating music based on DNA sequences as well as music based on protein amino acid sequences [2, 3, 4, 5]. In our work inspired by biological development we have been interested in the interactions between specific DNA sequences (i.e. genes). These gene interactions form what is known as genetic networks (Figure 1). One of the in- credible and inspiring aspects of biological development is the process of converting DNA sequence information into complex, hierarchical structure with repetition at different scales. An organism is composed of a variety of large-scale structures, some of which can be repeating structures like ribs and limbs. Each of these structures can be composed of a variety of tissues, which in turn can be composed of many cells of a particular cell type. Each cell, in turn, is composed of varied, but repeated, molecules. Similarly, a musical composition possesses complex, hierarchical struc- ture with repetition at different scales. A musical work might follow a sonata form or a rondo form composed of repeating sections and phrases. Within each of these larger sections, different rhythmic patterns, harmonic cadences, and melodic motifs can recur. Our work extends Susumu Ohno and Midori Ohno’s comparison of “repetitious recurrence” in music and biolo- gy to include the “repetitious recurrence” found in the complex hierarchical structures of both music and biology. With “Rhythm Zoo” we create “musical organisms” with musical form that is at once familiar and novel. We achieve this by creating algorithmically generated music modeled on the gene network dynamics that generate struc- ture in living organisms. “Rhythm Zoo” evolves from a nine-year investigation of biological systems as models for music composition, and is influenced by our backgrounds in evolutionary develop- mental biology, digital signal processing, music synthesis, art-science performance, and music composition. Figure 1. This is an example of a gene network [6]. Each node in the network represents a gene (e.g. ‘ftz’). At any giv- en time, a gene can be ex- pressed (ON) or unexpressed (OFF). The expression of a gene is dependent on influ- ences from other genes, repre- sented by the interconnecting lines. A gene can inhibit (turn OFF) the expression of anoth- er gene (red lines) or promote (turn ON) the expression of another gene (blue arrows). The in- terconnectivity of the network results in complex patterns of gene expression that are critical to defining structure and pattern in developing organisms. This particular gene network is important in defining body segments in the beetle Tribolium castaneum.