Simplify the following text for a Grade 8 native English-speaking person.
Original: Bull was one of the most famous composers of keyboard music of the early 17th century , exceeded only by Sweelinck in the Netherlands , Frescobaldi in Italy , and , some would say , by his countryman and elder , the celebrated William Byrd .
Simplified: Together with Sweelinck and William Byrd he was one of the great composers of keyboard music in the early 17th century .