In Advaita Vedanta, Om is the shortest and most powerful of Upanishads. The phonetic constituents of Om are the three letters. If you combine them, it becomes Om. Many people didn't know that, and then they know it over, and now I know it's actually Uma, and so I should pronounce it as Om. No, don't. Little knowledge is dangerous. O-M is absolutely correct. Om.
In this series of talks, Swami Sarvapriyananda unfolds the highest truths of Vedanta through the study of the Bhagavad Gita (The Song of God).