Simplify the following text for a Grade 6 native English-speaking person.
Original: Lauri Porra ( born December 13 , 1977 ) is a Finnish bassist best known for his work in Stratovarius and Sinergy .
Simplified: Lauri Porra ( born December 13 , 1977 ) is a Finnish bass guitarist . He is best known for his work in Stratovarius and Sinergy .