A somewhat-hidden instrument in one of New York's subway stations may be more than 20 years old, but it's still managing to delight New Yorkers as though it were brand new.

Venture underground into the 34th Street Subway station and you may notice a pair of forest-green pipes that don't quite blend in.

This is 'REACH: New York', a pair of tubes on the N/Q/R/W uptown and downtown platforms that 'sing' to each other across the tracks when prompted by playful commuters.

The urban musical instrument was installed at the 34th Street station by sound artist Christopher Janney in 1995.

But it's still a regular guest on the New York social media scene thanks to its wonderful ability to connect strangers from across the way.

Simply reach (or jump up if you're small) and wave a hand across one of the installation's eight 'eyes', and a beam of light is interrupted. This activates the instrument, which emits a range of sounds: from the marimba and the flute to the sound of the rain forest.

If someone on the opposite platform would like to respond, they can do the same on their end. Watch the video above -- posted to Instagram by @mrnycsubway this week -- to see how complete strangers are still using the piece to play while they wait for the train.