Oh how we wish we could've have witnessed this!

Legendary singer and actress Liza Minnelli delighted audience members at a New York City bar Sunday, when she joined musicians onstage for a surprise performance!

The Cabaret star was originally at Bemelmans Bar inside The Carlyle Hotel to support her friends, musicians Billy Stritch and Jim Caruso, who perform every weekend at the venue.

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According to Page Six, Liza took to the stage with pal Michael Feinstein for two songs, including "I Love a Violin," written by Liza's godmother, Kay Thompson.

The 68-year-old, who made a splash at this year's Academy Awards for wearing an all-blue ensemble, appeared to love the crowd's energy, declaring, "This is the best party in New York!"

Liza will reportedly be in the audience Friday evening for Cher's "Dressed to Kill" tour at Brooklyn's Barclays Center, which makes us wonder, will the divas join forces for a duet?