Simplify the following text for a Grade 9 native English-speaking person.
Original: During the 21 March 1967 session in which producer George Martin added a piano solo to Lovely Rita , Lennon complained that he did not feel well and could not focus .
Simplified: During the 21 March 1967 session in which producer George Martin added a piano solo , Lennon complained that he did not feel well and could not focus .