While flash mobs are often entertaining, they are not usually described as "classy." But classy (or rather classiness) is exactly what went down on a Copenhagen subway train last month. Members of the Copenhagen Philharmonic popped up alongside riders for an impromptu performance, brass and woodwinds included.

The train's commuters were facing yet another dreary trip to work, but instead they were treated to a performance of Grieg's 'Peer Gynt.' Check it out.

That subway has pretty good acoustics, doesn't it? And, as you can see, the horns and strings bring smiles to many of the straphangers' faces. The flash mob was a way of promoting the Philharmonic's 2012-2013 season.

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