Visualizing Bach: Alexander Chen’s Impossible Harp

"Music," Gottfried Leibniz famously said, "is the pleasure the human mind experiences from counting without being aware that it is counting." Computer artist Alexander Chen makes this pleasure visible with Baroque.Me, his geometric computer animation of the Prelude to Johann Sebastian Bach's Cello Suite No. 1 in G major.

Chen visualized the piece by imagining a harp with strings that would automatically morph into different lengths according to the principles of Pythagorean tuning. "It's math based on the fraction 2/3," writes Chen on his blog. "I started with the longest string, setting it to a symbolic length of pixels. When cut to 2/3 length, it goes up a fifth. Cut its length by 1/2 and it goes up an octave. 3/4 length, one fourth. From these simple numbers I calculated the relative string lengths of all the notes in the piece." He used eight strings because the Prelude's phrasing is in groups of eight notes. The strings are "plucked" by two symmetrical pairs of nodes that revolve at a uniform rate, rather like a digital music box.

Chen, 30, lives in Brooklyn, NY, and works in the Google Creative Lab. One of his most popular pieces for Google was the Les Paul Doodle, which allows users to digitally strum the guitar strings. Chen grew up learning music and computer programming in parallel. He plays the classical viola, but with the Bach animation he wanted to remove the performer's interpretive element from the music. "It's a piece that I've heard a lot since I was a kid," Chen told the BBC recently. (See the "Mathematical Music" podcast, Nov. 3.) "People always bring different levels of expression to it. People play to different tempos and they add a lot of dynamics, or less dynamics. But what I wanted to let the computer do was just kind of to play in a really neutral way, because what I really wanted to express was how much emotion and intensity is just in the data of the notes themselves. I think that's really where the beauty of the piece at its core is."

To hear the Prelude with the interpretive element back in, you can watch this video of Pablo Casals performing it in 1954:

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