In this paper, I analyze the musical content in Federico Alvarez del Toro's marimba concerto El Espiritu de la Tierra. This dissertation represents my analysis of features I hear in the composition, and does not reflect the composer's original compositional process. Commissioned by the governor of Chiapas, the piece was composed in collaboration with internationally renowned marimba virtuoso Zeferino Nandayapa and premiered in 1984 with the Philharmonic Orchestra of Mexico City at Festival Cervantino in Guanajuato. The work has not been published and has been mentioned only briefly in scholarship. Particular attention in the analysis is given to indigenous and folk idioms from the southern region of Mexico combined with post-modern compositional techniques. My primary argument within the dissertation is that I believe the piece demonstrates a respect for tradition and heritage while concurrently utilizing non-traditional and contemporary compositional techniques. Analytically, I argue that two basic shapes are used throughout the piece, and I argue that the many cultural references within the piece solidify a preoccupation with the lineage of southern Mexico.