Simplify the following text for a Grade 14 native English-speaking person.
Original: He had also conducted the Sunday afternoon radio broadcast when CBS listeners around the country heard the announcer break in on Arthur Rubinstein 's performance of Brahms 's Second Piano Concerto to update them about the attack on Pearl Harbor .
Simplified: He had also been conducting on the Sunday afternoon radio broadcast when CBS listeners around the country heard the announcer break in on Arthur Rubinstein 's performance of Brahms 's Second Piano Concerto to tell them about the attack on Pearl Harbor .