Simplify the following text for a Grade 7 native English-speaking person.
Original: Charlie Parker ( born August 29 , 1920 in Kansas City , Missouri ) , also known as `` Bird '' or `` Yardbird '' , is considered one of the greatest jazz saxophonists , specifically alto saxophonist .
Simplified: Charles Parker , Jr. ( August 29 , 1920 â `` March 12 , 1955 ) , famously called Bird or Yardbird , was an American jazz saxophonist and composer .