This essay is a musicological, analytical, and performance practice investigation of Variazioni e Toccata sopra “Aurora lucis rutilat,” op. 52 by Alberto Ginastera. Commissioned by and written for the Twin Cities Chapter of the American Guild of Organists, this piece was premiered during the National Convention of the AGO on June 18th, 1980 in Minneapolis, Minnesota, by the renowned American organist and pedagogue Marilyn Mason. Mason championed the composition for years on the concert platform, but the composition suffered neglect both by performers and scholars alike. Today, there exists not a single comprehensive study on this work, and only two recordings available. This essay seeks to clarify the composition by addressing 1) the relation between manuscript sources, the correspondence between composer and performer during and after the compositional process, recordings, and 2) by analyzing the form of the piece, by investigating its melodic relationship to the Gregorian tune, as well as by providing an examination of the text and its connection to medieval sources. I will devote a chapter to Ginastera’s biographical background, a review of the current scholarship, as well as a chapter devoted to the analysis of each single variation, thematic placement, and an overview of the harmonic relationship of endings.