This barbershop group were singing up a storm outside the Metropolitan Museum of Art in NYC. They were pretty great and a lot of people started gathering on the steps to watch.
The singers were very expressive, and warmed up my mood after I had been wandering around the city being assaulted by the wintry wind. I also heard some other great street performers during my brief visit to NYC, including the Subway Mariachi Band, who invaded subway carriages singing funny songs, and some amazing African drummers.
A quick search on YouTube showed that they are a regular fixture in the city.