Yesterday morning, 20 people lay on the floor of the Metropolitan Museum of Art and, to the surprise of museum visitors, began playing a dreamy song. The performance may have been the most beautiful flash mob ever to occur.

The 20-person ensemble plays under the name of Alarm Will Sound, a classical band that is currently undergoing a yearlong residency at the Met. For the flash mob, Alarm Will Sound played a supine version of British electronic musician Aphex Twin's "Cliffs." The group tweeted the performance yesterday morning.

On Saturday night at the Met, Alarm Will Sound played “Radio Rewrite,” a song by famed composer Steve Reich based on two songs by Radiohead. The group will next perform on Feb. 20 at the museum unless they decide to stage more impromptu flash mobs.

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