Simplify the following text for a Grade 9 native English-speaking person.
Original: On his 80th birthday , 18 July 2007 , Masur conducted musicians from both these orchestras at a Proms concert in London , conducting music by Tchaikovsky and Bruckner .
Simplified: On his 80th birthday , 18 July 2007 , Masur conducted musicians from both orchestras at a Proms concert in London .