Task: Sentence Expansion
Input (English): 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 .
Output (English): 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 .