Photo: Getty Images

By Sierra Marquina

Ryan and Ellen K. called Ken Ehrlich, producer of the Grammys and the The Beatles: The Night That Changed America – A Grammy Salute, which scored over 13 million viewers on Sunday night.

The special featured performances by everyone from Katy Perry, John Mayer, and Ed Sheeran to Keith Urban, John Legend, Pharrell, Imagine Dragons, and more.

Ken revealed it was easy to get the artists to participate, but “the only intimidation factor was [singing in front of Paul McCartney and Ringo Starr themselves].”

So which artist was the most nervous about performing the legends’ songs?

“Honestly, I think Katy [Perry] was,” Ken admits. “She was really concerned. I thought she killed on ‘Yesterday,’ I thought she really did a great job, but she was definitely kind of concerned about singing like the number one song in the history of music.”

And understandably so!