Since 2004, New York’s Improv Everywhere theatre group has run a series of MP3 “Experiments” through its website. Punters download an MP3, load it on to their iPods and turn up at the meeting point. At a given signal, they start the MP3 and follow the instructions. Hilarity ensues.

The first MP3 Experiment was in a theatre. A disembodied voice called Steve told the audience to get on stage for dancing, balloons and lots of high-fives. Eventually, they left and followed Father Christmas to a local bar. Apart from those who got lost when their iPods jammed, the audience enjoyed it.

Experiments two and three were in Central Park, featuring a mass rock-paper-scissors tournament and a 600-person-long conga line.

Experiment four was held in a park in lower Manhattan where 826 people in colour-coded T-shirts danced, made a huge human dartboard and sunbathed.

Improv Everywhere provide full instructions for holding your own Mp3 experiment. They've already inspired spin-off experiments from as far afield as Penn State University and Seoul, South Korea.

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