From the Lords of Initiation.

The Mantra given at the Initiation is an integral part of the process. It is used to unlock the potential for the Aspirant to ascend Spiritually into the Hightest Realms.
Often, when the Mantra is repeated before the Initiation the Seeker is able to access the Spiritual Regions.

After the Initiation it should be used at the beginning of each Meditation session to focus the Meditator. Meditation on the Light and Sound is a Gift which should not be taken lightly. Saying the Mantra will help the Meditator to make the most of the sessions.