Mantras are in the form of praise and appeal to the deities, craving for help and mercy. Some Mantras control and command the evil spirits. Rhythmical vibrations of sound give rise to forms. Recitation of the Mantras gives rise to the formation of the particular figure of the deity
From Amrita Gita by Swami Sivananda, copyright The Divine Life Society. Swami Sivananda was a self-realized Master and a very practical Guru. Following His teachings can lead you to the Absolute.