Simplify the following text for a Grade 9 native English-speaking person.
Original: The Three Choirs Festival , originating in the eighteenth century and one of the oldest music festivals in Europe , is held in Gloucester every third year , the other venues being Hereford and Worcester .
Simplified: The annual Three Choirs Festival , which started in the eighteenth century and one of the oldest music festivals in Europe , takes place in Gloucester every third year . The other places the festival is held are Hereford and Worcester .