Cristóbal Halffter, born in 1930, established himself as an important figure in Spanish avant-garde composition in the middle of the twentieth-century. As one of the prominent leaders of the Generación del 51, he helped establish modernity in music as a part of Spain's identity. His compositional style mixing tradition with the avant-garde was built on the success and breakthrough of Manuel de Falla, a composer with close ties to Halffter's family and served as a 'father figure' to the Generación del 51. This study begins with a discussion on Falla's work and reception, as he lay the groundwork for modernism in Spanish music. Further, discussion on Halffter's background and compositional periods, from his nationalist approach in the 1950s to his embrace of the avant-garde in the 1960s and beyond exemplifies Halffter's prominent role in shaping Spanish modernity. This research then sheds light on previously unexplored solo flute works Debla [Solo VI] for Flute and Studie II [Solo III] for Flute by Halffter. Provided is insight to their respective influences (the Spanish debla and the Fibonacci sequence), analysis of each work, and a discussion on their similarities and differences. By taking an informative approach prior to analysis and performance suggestions, readers will gain insight to Halffter's Spanish roots as they relate to nationalism and the avant-garde, his affiliation with the Generación del 51, and his compositional style.