Andrea Mandell

USA TODAY

On the eve of Election Day, Madonna turned up in Washington Square Park with a guitar, a handful of songs, and a heartfelt message about why she's advocating for Hillary Clinton.

"This is a concert about unifying us, and it's about keeping America great, not making America great," Madonna told hundreds of fans who swarmed as word spread of her surprise appearance. "This is a concert about peace, OK? And we are trying to elect — we are going to elect — a president that is going to keep America the great country that it is and has the potential to be."

The pop star performed a 30-minute set of five acoustic songs, including John Lennon's Imagine, upon which the crowd joined her for the chorus.

Madonna performed in New York as the Democratic presidential nominee took the stage at a massive rally in Pennsylvania, where Jon Bon Jovi and Bruce Springsteen performed and Clinton was introduced by President Obama.

Madonna also performed acoustic versions of Like A Prayer, Don't Tell Me, Express Yourself and Rebel Heart.