Vak (power of speech) sprouts in Para, produces two leaves in Pasyanti, buds in Madhyama, and blossoms in Vaikhari—that Vak, as previously mentioned, completes the stage of sound absorption, reversing the above order, namely, starting with Vaikhari, etc.

The four types of Vak are Para, Pasyanti, Madhyama, and Vaikhari. The strongest tone is para. Vaikhari is the most obnoxious of tones.

Vak progresses from the most high-pitched to the most low-pitched tones.

In order to merge in para, or the highest subtle tone, involution requires reversing the order.

Anyone who believes that the One who is the great Lord of that Vak, the undifferentiated, the Illuminator of that Vak is the Self is never affected by language, whether high or poor, good or poor.

You may also want to read more about Kundalini Yoga here.