The speech of the celestial angels abounds in the vowels A (ah, as in father), and U (as u in rule). One may often determine from the Hebrew vowels in a passage which words belong to the class of celestials and which to the spirituals — i.e., whether they involve good or truth. The former use more frequently the sounds of O and U, for they have a full tone, and also occur oftener in the Third Heaven. (Heaven and Hell 241; True Christian Religion 278;, Spiritual Experiences 5112, 5620, 5787)

5113. The cause of this is from no other source than the feeling arising from love, which is rich with sound, as also can be demonstrated by harmonies and musical instruments. When these express higher things of love, such as love to God, then too there must be a rich sound; likewise when they give expression to a devout feeling about God there is an almost bass sound. But when the feelings are about other things, these produce different sounds that harmonize with the related melody.