Marcelo Adonay (1848-1928) was a major Philippine composer and church musician. As maestro de capilla of the San Agustin church in Intramuros, Manila, he presided over the musical establishment of a powerful Augustinian Order that required the performance of elaborate instrumental and choral works. This pioneering work includes five major essays on Adonay's life, his milieu, an inventory of his extant and missing works, and musical and formal analyses of his magnum opus, Pequeña Misa Solemne sobre Motivos de la Missa Regia de Canto Gregoriano.