Antonio Francisco Javier Jose Soler was an eighteenth century Catalan composer, priest, monk, student, teacher, mathematician, inventor, and organist. His life was spent serving both the Catholic Church and music. He was a prolific composer with over 400 compositions credited to him by the time of his death at age 54. Soler spent most of his life at monasteries, particularly El Escorial, the magnificent royal palace, chapel, and monastery built by King Philip II outside of Madrid two centuries earlier. Soler apparently came from a musical family. His brother, Mateu, played bassoon in the monastery of Las Descalzas Reales and then in the court of Carlos III, and finally in the Capilla Real. His musical training began at a very early age. In 1736, he became a student at the Benedictine monastery choir school at Montserrat where he learned organ and composition. Between 1752 and 1757, while in his early twenties, Soler studied with Domenico Scarlatti, the Italian composer who served the Spanish court of Ferdinand VI and Maria Barbara. Prior to going to El Escorial, where he spent the rest of his life, Soler was the maestro de capilla at Lerida and was ordained subdeacon in 1752. Later that same year, he joined the Hieronymite order of monks at El Escorial monastery and professed to the order in 1753. Soler performed many duties at El Escorial. In 1757, he became maestro de capilla. In addition, he performed as first organist, wrote much of the church music, and taught music. Perhaps his most prestigious student was the son of Carlos III, Don Gabriel de Bourbon. Soler taught the young Don Gabriel keyboard and many of the Soler's harpsichord sonatas were written for him. It is difficult for most to grasp Soler's level of productivity, particularly in light of his many other duties and interests. His musical compositions included over 120 sonatas for harpsichord, six quintets for organ and strings, six double organ concertos, 10 masses, five requiems, 132 villancicos, and many other works. His most famous was a sonata for harpsichord entitled Fandango. Soler also wrote a treatise on harmony, Llave de la Modulación (1762) whose concepts remain valid today. This treatise, however, caused considerable controversy and rebuke by some of his peers. These criticisms caused Soler such dismay that in 1765, he responded with a written retort, Satisfacción a los reparos precisos, which spanned 67 pages and was supported by such noted authorities as Morales, Palestrina, and Scarlatti. The controversy did not end until a final defense was provided in Jose Vila's Respuestra y dictamen in 1766. He developed another treatise in 1771 that demonstrated his interest and skill in mathematics. This book was on Castilian and Catalan currency exchange and was published in honor of Carlos III. Soler was a man of other talents in addition to those mentioned. He invented a tuning box that was used to demonstrate differences between tones and semitones to Don Gabriel. He was also expert in organ design and construction. In 1776, he developed the specifications for an organ for the Malaga Cathedral.