Excerpt from the NAOS:
- Vibration:
Vibration implies that each part of the word to be used, (either alone or as part of a text or key) is resonated deeply and this requires the person to be standing and the ‘solar plexus’ to be used to generate the deep breathing required, the mouth acting as a resonant cavity. The vibration should be such that it is felt in the whole body - a vibration is not a shout or scream but rather a prolonged concentration of sound energy.
For example, to vibrate the word ‘Satan’. Take a deep breath and sound ‘Sa’, for the length of that breath (not less than twenty seconds) trying to maintain the same level of intensity as the breath fades - then inhale quickly and vibrate ‘-tan’ while exhaling the same manner as before. Practice will enable the length of each part to be increased. To obtain the required ‘depth’ or power, attempt to project the sound in front of you to a point at least ten feet away.
The essence of vibration is control of the sound - it should be as even as possible and the same on all parts of the word or phrase. With practice, the relative pitch of vibration can be altered, although this is not as important as producing a powerful vibration since most magickal vibrations require power rather than finesse of pitch.