The Harmonic Series is a collection of mechanical devices, software, sculptures and prints that explore and visual musical harmony.

This is an ongoing project by Manuela Donoso and Luisa Pereira. It is currently being shown at FILE 2014 in Sao Paulo, Brazil, and at the Bienal Kosice in Buenos Aires, Argentina. It will also be shown at the Dumbo Arts Festival in New York City from September 26 to 28.

This is an electronic and interactive reinterpretation of an experiment conducted by French mathematician Jules Lissajous in the nineteenth century. Where he used tuning forks, we used speakers, to allow user input.

The two speakers are placed inside a box, perpendicular to each other. Each has a small mirror attached to it. A laser is pointed at the first mirror, reflected by the second and finally projected on the top of the box.

As the speakers vibrate at the frequency of the voices, a representation of the interval between them is generated.

In the nineteenth century French mathematician Jules Lissajous invented a device to visualize sound vibrations. Two tuning forks were placed orthogonally, each with a mirror attached to its tip. A beam of light was directed to the first mirror, reflected to the second one and finally to a screen. If the frequencies of the tuning forks were related by simple integer ratios –which makes them harmonic musically– the figures would be visually harmonic as well.

Interested in the relationship between aural and visual harmony, we re-created and extended this experiment using current tools.

An electronic version of the device replaces the tuning forks with microphones and speakers, allowing people to sing different intervals –an octave, a fifth, a major third– and contrast the resulting figures with the more chaotic ones generated by percussive sounds.

Here are some of the images they generated captured by long exposure on photographic paper.