The purpose of this document is to further the current research and encourage interest in the music of the Mexican composer Ernesto García de León. This paper will advance the current research with an in-depth analysis of the first movement of Sonata No. I, Op.13, Las Campanas (The Bells) for solo guitar. The analysis will focus on the pervasive presence of the melodic and harmonic intervals of perfect fourths, perfect fifths, and tritones as constructive devises throughout the sonata. This will provide interested performers a technical understanding of the composition. In addition to the compositional aspects, the analysis will be extended to consider the programmatic elements described by García de León. Select alternative fingerings will also be given to provide the interpreter options for difficult passages.