U2 normally sells out arena around the globe, but the band played on a much smaller stage on Monday.

Bono and the band headed underground to give a surprise performance at the Grand Central subway station in New York City. The four Irishmen dressed as street performers and sang "Angel in Harlem" to a small gathering of riders by the 42nd Street S shuttle.

The Edge and Adam Clayton played their acoustic guitars while Larry Mullen Jr. swapped his drum kit for four buckets. The band even kept an empty guitar case open for tips (no word on what they actually did with the money they collected).

 #u2 #jimmyfallon #ny #metrostation #angelofharlem

A video posted by U2 italian fans (@u2italianfans) on May 5, 2015 at 12:28am PDT

The pop-up performance was part of U2's upcoming appearance on "The Tonight Show Starring Jimmy Fallon" on May 8, according to Entertainment Weekly. Fallon attended the performance and has been filming other fun segments with the band.

U2 appeared as Fallon's first musical guest when he took over "The Tonight Show" last year. They were scheduled to appear for a week's worth of shows in November, but had to postpone after Bono's bike accident that has left him unable to play the guitar.

U2 will kick off its "Innocence and Experience Tour" on May 14 at Rogers Arena in Vancouver, British Columbia.