Simplify the following text for a Grade 9 native English-speaking person.
Original: Leonard Bernstein ( , ; August 25 , 1918 -- October 14 , 1990 ) was an American conductor , composer , author , music lecturer and pianist .
Simplified: Leonard Bernstein ( August 25 , 1918 â `` October 14 , 1990 ) was an American composer and conductor .