Simplify the following text for a Grade 10 native English-speaking person.
Original: He has written eight numbered symphonies since , a Sinfonia Concertante ( 1982 ) , as well as the series of ten Strathclyde Concertos for various instruments ( pieces he wrote when he worked with the Scottish Chamber Orchestra ) .
Simplified: He has written eight numbered symphonies sinceâ '' a symphonic cycle of the Symphonies Nos. 1 â `` 7 ( 1976 â `` 2000 ) , a Symphony No. 8 titled the ` Antarctic ' ( 2000 ) , a Sinfonia Concertante ( 1982 ) , as well as the series of ten Strathclyde Concertos for various instruments ( pieces born out of his association with the Scottish Chamber Orchestra , 1987 â `` 1996 ) .