Aum can be chanted slowly or quickly. Each method is as good as the other and you must experiment yourself to find out your own preference. If it is chanted quickly, then it is a powerful method to synchronize it with the heartbeat. In this manner, you can feel Aum resonating throughout the whole body in tune with the natural heart rate. Under these circumstances, Aum seems to chant itself; if you wish you can imagine Aum emanating from the heart region. Another excellent method is to coordinate the Aum chanting with the pulse at the eyebrow centre. This again is very powerful and very conducive to introspection and relaxation, and eventually meditation. Fast Aum chanting is best done mentally and not verbally, for loud chanting will tend to drown out perception of the heartbeat or pulse.
If Aum is chanted slowly it can be made to last for many seconds, depending on the capacity of the individual. There should be a definite pronunciation of each of the syllables ‘A’, ‘U’ and ‘M’ with a gradual transition from one to the other. The syllable ‘A’ is pronounced like ‘AH’ or ‘a’ in the word ‘palm’. The syllable ‘U’ is pronounced ‘oo’ as in the word ‘room’. The syllable ‘M’ is not sounded by moving the lips like the usual ‘m’ sound. It is sounded after ‘A’ and ‘U’ like a humming sound: ‘m-mm-m-m-m-m-m-m’. This humming sound can be extended for as long as the practitioner wishes, but normally the ‘M’ sound should gradually taper off at the end of the chant.
Long Aum chanting can be both mental or verbal, though for most purposes verbal chanting is to be preferred. This particularly applies to beginners, for loud chanting or group chanting tends to more effectively calm a disturbed mind. And because most people have a mind that is in a continual state of conflict and turmoil, verbal chanting of Aum is generally preferable and most suitable for the majority of people. In a sense it overwhelms one’s mental attention. One is almost forced to concentrate on the sound and pronunciation of Aum, and the mind tends to forget its usual worries and mental distractions. This is why verbal Aum chanting is recommended for beginners, if it is possible. If it is likely to create problems by disturbing others in your house, then of course you must practise mental repetition of Aum.
As you make progress in yoga, then you can practise more and more mental Aum chanting, for this is most conducive to introspection, once your mind is reasonably relaxed. A particularly good practice is to first of all chant Aum verbally for sometime (the longer the better) and then change over to mental Aum chanting. This is a systematic method of withdrawing your awareness from the outside world and directing it inwards to explore the mind. It also systematically calms the mind.
You should pronounce Aum, whether mentally or verbally, so that it is a harmonious sound. It should come naturally without being forced. It is through continuous, melodious sound that the mind will become relaxed. It should be: “Like the continuous flow of an oil stream and like the vibration of a bell. This is the way to pronounce Aum and the way to really know the meaning of the Vedas.”
The pronunciation is so important. If you are still not sure then we suggest that you go to a local yoga school or ashram to hear the sound of Aum from people with experience.