Air added to the voice are produced at the vocal cord level, level 1. (see ’Various levels of the vocal tract’)
Air added to the voice usually gives an impression of intimacy and nearness, and is often used when you are singing quietly in Neutral within the microphone’s sphere 1 in which the microphone is held close to the mouth. For example, when the high frequencies from a breathy voice mix with the bass boost of the microphone, the broad, soft sound intensifies and gives ‘body’ to a frail and light female voice.
Air added to the voice is ONLY to be used in Neutral. Therefore, it can only be used at low volumes. Some think they have heard air added to a loud voice, but that is effects produced in recording studios and then added to voices to make them SOUND as if air is added to them, for instance a track with whispering of the song can be mixed with the metallic singing in loud volume. This may sound like the singer is singing with air on a metallic mode in a powerful volume, but one should not be deceived by this. Using added air in a metallic mode or at a powerful volume is unhealthy for the voice.
Air only appears on the voice when it passes through the vocal cords as the tone is produced. If too much air is allowed to pass, it may impair the efficiency of the cords and make the voice tired and the singer will run out of breath too quickly. By reducing the amount of air that passes and still preserve enough energy to produce the sound of added air whilst ensuring that the vocal cords are free to work, the added air does not harm the voice. It is possible to sing with air added to all parts of the voice, in all sound colours and on all vowels, but only in Neutral.
If using distinct twang together with air it can magnify the impression of air.