When Erik Tawaststjerna completed his multi-volume study of Jean Sibelius (1865-1957) in the late 1980s, it was anticipated that it would become the definitive source for information about the life and music of Finland's most revered composer. While there is no denying the musicological significance of Tawaststjerna's contribution, one nevertheless searches in vain among the pages of this monumental work for any discussion of Sibelius's association with Freemasonry or his "Musique religieuse" (opus 113). Prior to 1998, only one study of Sibelius's Masonic music had been published. It was written by Einari Marvia in Finnish, a language not readily accessible to most scholars. It therefore seemed appropriate to publish, in English, another study of this work, one that would draw not only from Marvia's research but also from a number of newly discovered documents. The author's first edition of Sibelius and His Masonic Music (1998) and its supplement (1999) has now been revised and presented here in a single volume. Those who have expressed an interest in discerning Sibelius's views of religion will find this study offers considerable information about that aspect of the composer's life. Opus 113 had become for him an expression of his belief in the universality of the Divine, a belief given credence in the beauty and wonder of nature.