Simplify the following text for a Grade 5 native English-speaking person.
Original: Herbert von Karajan , who in his early years was FurtwÃ ngler 's most detested rival , maintained throughout his life that FurtwÃ ngler was one of the great influences on his music making , even though his cool , objective modern style had little in common with FurtwÃ ngler 's white-hot Romanticism . The conductor who probably most clearly represented a continuity with FurtwÃ ngler 's incandescent style was Jascha Horenstein , who had worked as an assistant to FurtwÃ ngler in Berlin during the 1920s .
Simplified: FurtwÃ ngler gave the most famous concert of his career in 1951 .