Playing piano in Madison Square Park

To find the piano in Madison Square Park, just listen for the cacophony of children plonking on the keys.

The instrument, located in the playground’s northeast corner, is one of 60 upright pianos placed throughout the city yesterday as part of “Play Me, I’m Yours,” a public art project by London artist Luke Jerram.

At the park, kids approached the piano with varying intentions — some flitted up and bashed the keys between rides down the slide while others methodically picked out patterns. They shared the piano, with at one point five children playing (not quite) together.

But then things got really interesting. amNewYork brought along a special guest: Brooklyn pianist Gabriel Kahane, a musician well versed in both classical and pop realms.

When he took up behind the keys, he started with the Allemarde from the E-flat French Suite by Bach. The kids were transfixed, and even their parents came over to listen. The sound didn’t travel too far, but those within earshot were cheered by the unexpected performance.

A small, all-ages crowd gathered as Kahane played Variation 1 of Bach’s Goldberg Variations, as well as his own composition “Durrants,” from his self-titled 2008 pop album.

When he finished, the children — who had been leaning on, and in one case sitting under the piano — approached Kahane in a way that the adults were too shy to do.

One requested, “Do you know ‘New York State of Mind’?”

Kahane did, of course, but by that time the keyboard was already swarmed again with children making their own music.

“Play Me, I’m Yours” runs through July 5. Visit streetpianos.com/nyc2010 for a map of all pianos’ locations.