How did One Direction celebrate their win for Best Summer Song at Sunday night’s Video Music Awards? By breaking out in tune at a star-studded after-party.

A guest at the post-show bash held at NYC’s Soho Grand Hotel tells Wetpaint Entertainment that the hands-down highlight of the party was the guys from 1D teaming up with Bruno Mars and Ellie Goulding in a rendition of Mars’ hit, ‘If I Was Your Man.’

“Bruno was at the house piano with One Direction and Ellie accompanying him,” the partygoer tells Wetpaint. “It felt like we were at our own VIP concert.”

Hmm, 1D and Ellie Goulding singing together? We can’t imagine a better British Invasion taking place these days, but we’d be remiss if we didn’t point out the opportunity for rumored flirters Ellie and Niall Horan to, ahem, harmonize. The two reportedly kissed at a recent music festival, though Ellie is in a relationship — and she even held hands with pal Ed Sheeran at the VMAs!

In other One Direction relationship fodder, Harry Styles’ ex, Taylor Swift — who took home the award for Best Female Video — was in attendance at the after party, but shied away from the singing part of the late hours.

Notes the guest, “She and Harry took a few group pictures together, but other than that, they didn’t interact much. Taylor spent most of the night hanging with Selena [Gomez]. They seemed to be having a girl’s night out.”