Limpidity of OM as A-U-M

Om is considered a mystical sound. An entire upaniṣad [1] delves into its significance. But its physical experience as the split-sandhi a-u-m is incredibly limpid.

Try this little vocal exercise:

1. Relax your jaws, cheeks, and lips completely.
2. Open your mouth wide by letting the lower jaw come all the way down.
3. Inhale deeply for an extended, gentle, exhalation. Exhale gently and make a relaxed aaaa sound. (Any other sound will move the lips or the jaws)
4. Gently bring up the lower jaw, keeping the throat and lips relaxed.
5. Let the sound continue.
6. Listen to the change in the sound. When the lower jaw is midway, the sound changes clearly when the vibration has shifted from the back to the middle of the mouth.
7. Let the lips touch and let the sound die out.

The sound changes, effortlessly and naturally, from aaaa to uuuu to mmmm!

Try recording yourself and playing back.

Now, try it at a higher pitch, and bring up the lower jaw faster. But keep the lips completely relaxed to avoid shaping the sound. The change in sound should come from the jaw movement alone.

It's a really nice way to understand why Aa to mm is considered the full range [2] of vocal sound, from the very back to the very front.

NOTES

[1] The māṇḍukya - albeit the shortest upaniṣad at just 12 shlokas!

[2] The plosives - consonant sounds with the lips - require lip movements, while mmm doesn't. So one can argue that mmm is the last sound possible even if it isn't the last letter of an alphabet (Sanskrit, e.g.).