Simplify the following text for a Grade 9 native English-speaking person.
Original: On April 16 , 2007 , Gustavo Dudamel conducted the Stuttgart Radio Symphony Orchestra in a concert in commemoration of the 80th birthday of Pope Benedict XVI , with Hilary Hahn as solo violinist , with the Pope himself and many other church dignitaries among the audience .
Simplified: On April 16 , 2007 , Gustavo Dudamel conducted the Stuttgart Radio Symphony Orchestra in a concert to celebrate the 80th birthday of Pope Benedict XVI , with Hilary Hahn as solo violinist . The Pope was at the concert .