Indian classical music originated from the Vedic hymns of Aryan religious rituals. The so-called "Vedic hymn period" in the history of Indian music is approximately between the 16th century BC and the 4th century BC. Among the four Vedas mentioned above, the Rig Veda contains 1,028 poems, some of which are myths and legends, and some of which are descriptions of natural phenomena and social reality. Sama Veda is a collection of songs sung to music. The Yajurveda explains how to use these songs for priestly conduct. When singing, the designated Brahmin priest sings in three tones: high, medium and low.