By first chanting out loud with lots of enthusiasm, the physical, mental, and emotional energies are engaged. As the chanting becomes quieter, we are drawn away from the outward perimeter of our consciousness into a more inward state of mind: Our many thoughts become drawn to a focus on the one thought of God, the body becomes still, the heart beats more slowly, the breath becomes nearly imperceptible - attention is focused at the spiritual eye.
As the chanting draws to a conclusion, the words and music have moved from being an external experience to an internal one; there is a dynamic stillness that can be tangibly felt. At this crucial moment, we have the opportunity to take the vibration set up by the chanting and dive deep into meditation.
Talking or physical movement of any kind can collapse the delicate vibration that has been set up by the music, destroying the subtle, but very real, effect that chanting has created. If we think of chanting as a part of meditation, and not as something that happens before the real meditation begins, it is easy to set the scene so that individuals meditating alone or groups of people meditating together can receive the full benefit.
Prayers, an introduction to the proceedings, even the double breathing and tensing and relaxing exercises can be done before the chanting begins so that [you] can go directly from chanting into the silence of meditation.
Source: Ananda.org
Also read these ebooks:
Aleister Crowley - Book 4 Part I MeditationAlan Wallace - Lucid Dreaming And Meditation