The guitar chord (a sonority based on the open strings of the guitar) is one of Alberto Ginastera's compositional trademarks. The use of the guitar chord expands throughout forty years, creating a common link between different compositional stages and techniques. Chapters I and II provide the historical and technical background on Ginastera's life, oeuvre and scholar research. Chapter IV explores the origins of the guitar chord and compares it to similar specific sonorities used by different composers to express extra-musical ideas. Chapter V discusses Ginastera's initial uses and modifications of the guitar chord. Chapter VI explores the use of the guitar chord as a referential sonority based on Variaciones Concertantes, Op. 23: I-II, examining vertical (subsets) and horizontal (derivation of motives) aspects. Chapter VII explores uses of trichords and hexachords derived from the guitar chord in the Sonata for Guitar Op. 47.