What is a mystery? Perhaps it is something that is difficult or impossible to understand or explain. David Thompson states that “the origin of this Nativity poem is in itself a great mystery. It is not a biblical text.” In the eleventh century, this text appeared as responsories for Matins on Christmas morning, but because the text is not biblical, there is much more leeway in how the words can be used in musical settings. Composer Evan Ramos creates mystery in his setting of O Magnum Mysterium through the use of dissonant clusters and by employing specific chord progressions that result in tension and release.