Taylor has one song which is a surprise to her fans each night at her "Eras" concerts, and Saturday's was "Dear John"-- a biting song about ex-flame John Mayer.

Taylor clearly had bad feelings about John when she wrote the tune, but on Saturday her tune changed. She told the crowd, "I'm 33 years old. I don't care about anything that happened to me when I was 19. I'm not putting this album out so you can go on the internet and defend me against someone you think I wrote a song about someone 14 million years ago."

Taylor explained she was re-recording "Speak Now" which includes "Dear John" because she wants to own her own music, but she clearly says she's not interested in trashing him.