Q: Can Om only take one so far in the direction of Self-realization? Should Om be let go of at a certain point, or is the practice retained? Can a still and silent mind be achieved if there is still Om with the breath even if it is very subtle? In my practice the intonations of Om have softened and become like a wisp of smoke that is almost indistinguishable and inseparable from the breath–even indistinguishable from the breath.
In the scriptures that deal with yoga and meditation, such as are cited in Om Yoga Meditation and The Word That Is God, Om is declared to be both Brahman and the Self. Self-realization is the realization of Om as the Self and Brahman–the individual Self (jivatman) and the Supreme Self (Paramatman). Om is itself the revelation of Brahman and the Self.
Therefore there is no question of letting go of Om in meditation. Rather, as you have experienced for yourself, in meditation (and outside as well) the japa of Om becomes increasingly subtle just as you have described. And in time that is experienced not just as the movement of the breath, but as consciousness itself. For Consciousness and Sound are discovered to be the same, as Purusha and Prakriti are the same–not two. Therefore the Chandogya Upanishad (1.5.3) says: “The breath is continually sounding Om” because the two are one.
Q: While being with Om and the breath I have also focussed on letting go of thoughts, feelings, etc. Obviously, there is a way to go in that practice and I am seeking your advice.
There is no need to think of letting go of thoughts, feelings, memories and suchlike. Instead just relax into the mental sound of your intonations of Om and let Om fill your entire awareness.
I hope you will occasionally reread or skim through Om Yoga Meditation [on our website] to keep these ideas vivid in your mind.
Note: Om Yoga Meditation: Its Theory and Practice is also available in print and as an ebook at Amazon.com