The seven vowels, which we use every day in speech, are truly mysterious things. Analysis shows that vowels depend on the phenomenon of harmonics, which is at the very basis of music, while our sensitivity to them proves that the human ear is naturally attuned to harmony. When we hear vowels, we are hearing the laws of harmony, which are ultimately the laws of number that are said to govern the universe. There is also an esoteric tradition that links the vowels to the seven planets of astrology and the gods that rule them. The mythological background includes such topics as the vowel-names of IAO, IAHWE, and other gods; the invocations of planets used in Egyptian temples and in Greek magical incantations; the power of wordless song to illuminate and heal, and even -- if the reports of occultists are true -- to aid the soul after it has left the body. This is the first book on the subject ever to appear in English, and it is unusual in bringing together a number of fields not usually connected: linguistics, harmony, musicology, mythology, the history of religions, esoteric and occult philosophy, vocal exercises and meditational practices. The author discusses systems relating the vowels to planets, tones and colors; he writes of ancient and modern vowel-songs, the names of the gods, and the use of vowels in Gnosticism and ancient magic. The treatment is scholarly, but the book is also practical, giving a number of different paths for discovering one's own tones through the vowels, and exploring their power to center, to uplift, and to heal. Joscelyn Godwin is Professor of Music at Colgate University. He is the author of Harmonies of Heaven and Earth, Robert Fludd, Mystery Religions in the Ancient World, and many other books and translations relating to the Western esoteric traditions.