The Planetarium as a Musical Instrument Dale E. Parson Kutztown University of PA 15200 Kutztown Road Kutztown, PA 19530-0730 parson@kutztown.edu Phillip A. Reed Kutztown University of PA 15200 Kutztown Road Kutztown, PA 19530-0730 preed@kutztown.edu ABSTRACT With the advent of high resolution digital video projection and high quality spatial sound systems in modern planetariums, the planetarium can become the basis for a unique set of virtual musical instrument capabilities that go well beyond packaged multimedia shows. The dome, circular speaker and circular seating arrangements provide means for skilled composers and performers to create a virtual reality in which attendees are immersed in the composite instrument. This initial foray into designing an audio-visual computer- based instrument for improvisational performance in a planetarium builds on prior, successful work in mapping the rules and state of two-dimensional computer board games to improvised computer music. The unique visual and audio geometries of the planetarium present challenges and opportunities. The game tessellates the dome in mobile, colored hexagons that emulate both atoms and musical scale intervals in an expanding universe. Spatial activity in the game maps to spatial locale and instrument voices in the speakers, in essence creating a virtual orchestra with a string section, percussion section, etc. on the dome. Future work includes distribution of game play via mobile devices to permit attendees to participate in a performance. This environment is open-ended, with great educational and aesthetic potential. Keywords aleatory music, algorithmic improvisation, computer game, planetarium 1. INTRODUCTION & RELATED WORK This project grows out of the intersection of prior work in mapping two-dimensional computer board games to music [9,10] and the availability of a modern planetarium with a high- resolution digital projector, a high-quality surround sound system, seating for 85 people and very good acoustics [4]. The predecessor to the current game-as-instrument is a computer Scrabble ® game extended to generate MIDI note and control information based on game rules and the progressing state of play [9]. The key musical aspect of that game is its mapping of statistical regularities in letter distributions in a game to statistical regularities in musical interval distributions in the scales being generated on MIDI channels. For example, in a typical player-configurable scale, common letters such as ‘E’ or ‘A’ map to consonant intervals such as the tonic or fifth in a channel’s scale, less common letters map to less consonant intervals, and outlying letters such as ‘Q’ or ‘Z’ map to chromatic passing tones. Players select game tiles pseudo- randomly then impose lexical structure on them by creating words that map to unique sequences of intervals. Other parameters for mapping placed letters to properties such as meter, tempo and timbre are under more direct control of a performing musician via a graphical user interface. The inspiration for writing a music-generating game specifically for the planetarium came at a computer music seminar in our facility on September 7, 2011 [7]. Dr. Michael O’Bannon of Atlanta provided excellent improvised video accompaniment for that event. Both the visual and acoustic properties of the facility were so good that the idea of adapting the graphical game-to-music approach to the planetarium presented itself as a natural next step. Several related projects involving generating music from the rules and states of games have influenced this effort [1,5,13,15]. Two additional influences are work on creating audio productions that are portable among planetariums [2], and an overview of problems for spatial sound from a two- session morning on the subject at ICMC 2011 [3]. In the current project we retain and extend the successful properties of the Scrabble game while replacing the game itself with one designed for play on a planetarium dome with circular seating. We abandoned an initial attempt at a word game because the geometry of a planetarium renders words upside- down and backward for many viewers. We settled on a game metaphor more suited to a planetarium, that of an expanding universe of atoms, where 12 distinct atomic numbers map to 12 distinct intervals in the current scale on a MIDI channel. By regulating the range and distribution of atomic numbers that they inject into the expanding universe, players regulate the degree of consonance / dissonance in the generated music. More complex musical properties emerge from aggregate game state as discussed below. We have had two successful ensemble performances by a faculty member and students to date, one at the Kutztown University planetarium on March 20, 2012, and another at a regional computing conference in southern Pennsylvania on March 30 [6]. 2. VISUAL ASPECTS OF THE GAME Our ensemble performances have consisted of two students playing the game via wireless networking and one of the authors manipulating musical mapping parameters. Game play consists of injection of atoms into the universe and manipulation of statistical properties of their elements. In addition to conventional graphical controls for atom injection and music translation, performers use live coding in the Jython dialect of the Python programming language [8] to automate portions of play. Figure 1 shows a screen shot of an early universe, before expansion, in which players have injected a variety of the 12 element types. An atom appears as a hexagon – we chose this geometry in order to accomplish symmetric tiling of the dome, naming the game HexAtom. Each distinct element type maps to Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. NIME’12, May 21-23, 2012, University of Michigan, Ann Arbor. Copyright remains with the author(s).