One of the most important ways to understand Olivier Messiaen’s musical language is through the lens of the theological ideas that many of his works convey. He considers expressing his Christian faith to be the primary purpose in his music. Through his idiosyncratic technique, Messiaen gives power and life to his religious music that he combines with his interest in literature, musical analysis, poetic imagery and symbolism, his love for theatre, and his compositional and organ abilities. The abundant studies of Messiaen’s works deal with the intricacies of his musical language, yet most of these studies barely discuss his theological ideas. Nevertheless, technical analysis of his music poses immense challenges, especially in the domains of melody and harmony. Although my approach is unconventional and do not follow any existing system, I base my technical and theological analyses mainly from Messiaen's technique, his commentaries and his references to the Scriptures. The “Combat de la mort et de la vie” is the heart of Les Corps glorieux in both technical and theological aspects. It is an intricate musical artwork where Messiaen demonstrates his melodic and harmonic developments using his idiosyncratic language, and through symbolism portrays the most complex of all drama according …