There's a lot of confusion concerning correct pronunciation of AUM.
It's actually very simple.
Open your mouth, relax your jaw.
Let the naturally occurring sound emerge, in an even tone, with no attempt to manipulate it.
Slowly, even, close your mouth, until your lips touch.
Uhh Oo M
AUM.
The exact vibrational resonance is created by, and therefore for, your specific body-mind system.
Just like Amaroli.
Only with less need for paper towels if you make a mistake.
Heart is where the AUM is,
Kirtanman
PS - Any use of the AUM mantra outside of suggested AYP guidelines is purely at the discretion of the individual practitioner; this post is for informational and/or entertainment purposes only. Ipso Facto. Yadda Yadda. Aum Namah Shivaya.