Q: You mentioned the "profound vibratory quality" of the sound I AM. What does this mean? If I choose to meditate on any sound I like, will it work just as well?
A: Certain sounds resonate in our nervous system. Deep in the silence of the mind they have a vibratory footprint that awakens our nervous system in particular ways. I AM is such a sound. As you continue to practice, you will see that your nervous system is being awakened in a particular way. It will be self-evident. You will say, "Ah Ha," because it will be obvious. When we learn advanced pranayama (breathing) methods, we gradually begin to see and feel the mantra unfolding the subtle nerves. So many flavors of bliss. That is when the profound vibratory quality of the sound becomes obvious.
So there is a method to the mantra. It is not just any sound. Still, you can meditate using any sound you like. If you use the sound, "banana," you will be able to take it to very silent levels of mind. But there is no guarantee you will not end up with bananas growing out of your ears. Only kidding…
As you become advanced, you will know exactly what the mantra is doing as it vibrates through your subtle nerves, spreading out inside your vast ecstatic regions. As you become familiar with your cosmic realms, options for using certain kinds of sounds, and also thoughts with meaning, will become apparent. But we must take it one step at a time. Today the mantra, tomorrow the cosmos. It all belongs to you.
It is all you.
The guru is in you.
Note: For detailed instructions on deep meditation, see the AYP Deep Meditation book.