Simplify the following text for a Grade 10 native English-speaking person.
Original: The petitions at the end of the hymn ( beginning Salvum fac populum tuum ) are a selection of verses from the book of Psalms , appended subsequently to the original hymn .
Simplified: The petitions at the end of the hymn ( beginning Salvum fac populum tuum ) are from verses from the book of Psalms , added to the original hymn later on .