A Brazilian living in London, Lizzie Bravo was one of the fans who used to congregate outside Abbey Road Studios in London during the late 1960s.
She is publishing her diaries from that time in a book, "From Rio to Abbey Road," and recently told the BBC about her guest spot singing backup vocals on "Across the Universe."
"We were outside the studio as usual. Paul simply came outside and asked if any of us could hold a high note," Ms. Bravo told BBC Brasil.
"I immediately raised my arm, as I was a soprano at my school choir back in Rio de Janeiro. But I had no idea why Paul asked that."
"The four of them were there recording this song," she said.
"All of a sudden I was hearing instructions from Paul and John about the part they needed us to sing. I was sharing the same microphone as Paul and John, who had always been my favorite Beatle."Fellow fan Gayleen Pease was also selected to sing on the track.