Arrangements of music from other instruments have always played a key role in expanding the guitar repertoire. This project investigates the life and work of eighteenth-century composer Antonio Soler (1729-1783), specifically his sonatas for solo keyboard. This study carries out a formal inquiry on Soler's influences, including a background of Soler's life and training, his connection with Domenico Scarlatti (1685-1757), and an overview of the eighteenth-century sonata in Spain. Timbres, articulations, tessitura, and other aspects of Spanish folk music are discussed as related to Soler's composition style. Five sonatas are analyzed in connection to Spanish folk music, and part of this study's focus was arranging the sonatas for two guitars: R. 48, 50, 60, 106 and 114. An overview of the current arrangements of Soler's sonatas for guitar is included in Appendix A.