The Vedas form the sound-manifestation of Ishwara, the non-decaying reality. This sound has four divisions: para which finds manifestation only in prana, pashyanti which finds manifestation in the mind, madhyama which finds manifestation in the senses, and vaikhari which finds manifestation in articulate expression. These four are the various gradations of sound. They are the gradual and materialized expressions of the transcendental voice. The Lord manifests himself through his power of maya first as para vani in the mooladhara chakra at the perineum, then as pashyanti in the manipura chakra at the navel, next as madhyama in the heart and then eventually as vaikhari in the throat and mouth. This is the divine descent of voice.
The highest manifestation of sound energy, the primal voice, the divine voice is para. The para voice gives birth to root ideas or germ thoughts. It is the first manifestation of voice. In the para state the sound remains in an undifferentiated form.
Yogis who have subtle inner vision can experience the pashyanti state of sound. Sound is associated with colour and form and accordingly the pashyanti state of sound is an object of internal vision. This is the reason why it is called pashyanti (from the root pashyat, one who sees).
The more we trace the inner origin of different languages we are approaching the vibrating homogeneity of sound behind them. Birds, beasts, Indians, Africans, Americans all experience the same feeling of a thing in the pashyanti state of sound. As one and the same shakti working through ears becomes hearing, through the eyes becomes seeing, and so forth, so also the same pashyanti experience assumes different forms of sound when materialized.
Madhyama is the intermediate unexpressed state of sound experienced in the heart.
Vaikhari is well known to us. It is the articulated sound, the last and grossest expression of divine sound energy. However, all vaikhari sounds are His voice only. It is the voice of the Virat Purusha. He as paratpara, the transcendental, stands beyond and above all states of consciousness and sound, and with mere will sets the vibrations of sound in motion to extend them on to the grosser planes. To us on the physical plane, this divine voice of His is known as vaikhari or the physical speech.
The divine voice is expressed in the lower planes in the above four ways. But there is another expression of His voice: the music of the spheres. This is created by the rotation of the whole universe, the earth, moon, sun, stars, satellites, etc. Like the sweet humming sound of a top set in brisk motion, all these bodies similarly rotate on their own axis, and thereby the music of the spheres is created. This, too, is His voice. Though inaudible to human ears, it exists at all times and everywhere. Sages and yogis can hear it. If the heart is simple and receptive, you too can catch the subtle vibrations of that universal sound.