A seriously good classical quartet recently setup and played in the 8th Ave subway station, and YouTube uploader mdthahir was there to capture it on video. Near the end of the piece, a group of ballet dancers joins in and starts to draw a crowd.
I am no expert on Classical music so I can't confirm, but SoundHound identified the music as Bach's Brandenburg Concerto No. 3.
via YouTube
Something wrong with this post? Let us know!