Mysterium Cosmographicum is a musical chronicle of an astronomy treatise by the German astronomer Johannes Kepler (1571-1630). Kepler's Mysterium cosmographicum (Tubingen, 1596), or "Secret of the Universe," was a means by which he justified the existence of the six planets discovered during his lifetime. Kepler, through flawless a priori reasoning, goes to great lengths to explain that the reason there are six and only six planets (Mercury, Venus, Earth, Mars, Jupiter, and Saturn) is because God had placed one of the five regular solids (tetrahedron, cube, octa-, dodeca-, and icosahedron) around each orbiting body. Needless to say, the publication was not very successful, nor did it gain much comment from Kepler's peers, Galileo Galilei (1564-1642) and Tycho Brahe (1546-1601). But hidden within the Mysterium cosmographicum. almost like a new planet waiting to be discovered, is one of Kepler's three laws of planetary motion, a law that held true for planets discovered long after Kepler's life-time. Mysterium Cosmographicum is a monologue with music in three parts for orchestra, narrator/actor, and computer music on tape. All musical data structures ape generated via an interactive Pascal computer program that computes latitudinal and longitudinal coordinates For each of the nine planets as seen From a Fixed point on Earth For any given time Frame. These coordinates are then mapped onto selected musical parameters as determined by the composer. Whenever Kepler reads From his treatise or From a lecture or correspondence, the monologue is supported by orchestral planetary data generated From the exact place, date, and time oF the treatise, lecture, or correspondence. To the best oF my knowledge, Mysterium Cosmographicum is the First composition ever written that employs planetary data as a supporting chronology to action and monologue.