This is SO well done.
A New York orchestra pitched up on a street corner and simply put a sign up saying 'Conduct Us', and then filmed the results.
Back in 2013, Ensemble ACJW (a joint venture between New York's Carnegie Hall and The Juilliard School of music) set up something special in collaboration with an organisation called Improv Everywhere.
According to the video's YouTube page, "Random New Yorkers who accepted the challenge were given the opportunity to conduct this world-class orchestra. The orchestra responded to the conductors, altering their tempo and performance accordingly."
The video shows a variety of different people stopping to conduct the ensemble in a performance of the overture from Mozart's The Marriage of Figaro.