Input (grade 10): Chants of the Office, sung during the canonical hours, have their roots in the early 4th century, when desert monks following St. Anthony introduced the practice of continuous psalmody, singing the complete cycle of 150 psalms each week.
Output (grade 10): Chants of the Office started in the early 4th century, when holy men in the deserts started the tradition of singing all 150 psalms every week.