Human harp makes music by playing the Brooklyn Bridge

[Nipuna]

[media]https://www.youtube.com/watch?v=z9aavje9H6E[/media]

Daredevils are not the only ones using bridges for fun: musicians are getting in on the act too. Di Mainstone and her team at Queen Mary University of London are attaching people clad in a special body suit to architectural structures with strings that tap into a building's vibrations and can be played like an electronic harp.

Mainstone was inspired by the Brooklyn Bridge while living in New York. "I wondered whether there was a way to capture the vibrations that go through cables triggered by walking, traffic and wind," she says. Since the vibrations aren't audible, they need to be transformed into a form we can hear.

To create her first prototypes, Mainstone hacked retractable dog leads that could be clipped to a person and pulled and plucked to make music. It evolved into a similar-looking device but with sensors to measure the movement of the strings and transmit the data wirelessly to software that converts it into sound.

This video shows an early version used last year for the anniversary of the Brooklyn Bridge. It wasn't yet able to harness the 'voice' of the bridge so the team chose representative sounds, which were modified by the movement of the strings. Soon after, Mainstone returned with microphones to record the bridge's real vibrations. Once processed, they produced a strange droning sound that included some harmonies. "It was magical and beautiful," she says.

The latest version of the system is being trialled at the Roundhouse in London, a circular venue once used as a railway engine repair shed. By mounting tiny hammers, similar to those in a piano, on the columns inside the space, they plan to capture sound from the beams, influenced by their hollow structure and material.

Later this year, the team will perform at the anniversary of the Clifton Suspension Bridge in Bristol, UK. They've already been able to extract the bridge's droning sound with accelerometers used by civil engineers to monitor new structures. Next, they will look at whether the bridge's 12 suspension cables of different lengths vary in pitch, as they expect them to. "The bridge is essentially a giant harp," says Mainstone.

The Human Harp installation will be at the Roundhouse in London until August 24.