Simplify the following text for a Grade 9 native English-speaking person.
Original: The Prelude and Liebestod is a concert version of the overture and Isolde 's Act 3 aria , arranged by Wagner , which was first performed in 1862 , before the first performance of the opera itself in 1865 .
Simplified: The Prelude and Liebestod is a concert version of the overture and Isolde 's Act 3 aria , `` Mild und leise '' . The arrangement was by Wagner himself , and it was first performed in 1862 , several years before the premiere of the complete opera in 1865 .