Press Play — "Live from Amma Cafe"
new playlist featuring Patch+, ear, Autobahn, Laetitia Sadier & more....
Let’s take a moment to look at sound.
Visual artist Lucio Arese has created three dimensional maps of bird songs. He has posted videos of his observations on Instagram:
In the above video, a fascinating dance takes place. Two birds sing in proximity to one another, and visualized as a progressive series of data points, their songs collide and circle around one another, as if the birds were flying, darting, fighting in the air.
The Y-axis measure amplitude (loudness or, for the sake of simplicity, volume).
The X-axis measures the “spectral centroid” of the recording. This is a mathematical approximation of timbre, a term that encapsulates a particular sound’s tonal qualities, which include qualitative descriptors such as brightness, coloration, and modulation. You can sort of intuitively grasp what these terms mean. A flute is “bright”, for instance. The value of the centroid is a moving weighted average, because a single “note” of a bird song, or any instrument for that matter, is in fact not a single frequency, but a spectrum of frequencies containing a central pitch as well as a harmonic series of overtones. Averaging them allows the data to be captured in a single point, which is useful for Arese’s tool, because accumulated over the duration of the song, these points paint a three dimensional picture of the sound’s journey that is arguably more descriptive than say, transcribing them onto sheet music.
But Arese is using a latent space analogy. Things are moving around in manifolds, not just rising and falling lines. What else is captured in the visualization?
This video explains things fairly well: the depth layer measures the “spectral crest”, a ratio of the spectrum’s peak versus its centroid. So the three variables at play are how loud is a given song note, where its central frequency lands, and where these individual notes fall in terms of stress or accentuation, together forming a narrative flow that is, at the very least, pleasing to see.
In the process of reading about Arese’s work, I learned songbirds produce vocalization via a syrinx. Instead of the vocal “chords” used by mammals—a construction of cartilages and muscles that vibrate and stretch to different lengths, somewhat analogous to vibrating strings—the syrinx is a bony, bifurcated chamber that resonates, like a pipe in a tiny church organ. By modulating the flow of air through this chamber, the bird can control pitch, even to the point of mimicry of human speech.
To summarize: birds are horns, humans are cellos. I think.
A horn and a cello don’t sound the same. This is timbre. The physical interaction with a resonant body is an explosive activity. Sound erupts from the chamber in every direction, with all the phantasmic stochasticity of pure physics. It is unwieldy, violent, and difficult to control. Exactly how such a frequency blast is interpreted depends on everything it bounces off, as well as the shape of the receiver. This is why throats, tubas, cellos, ears too, they all look kind of weird and loopy.
Perhaps through constructing these structures of timbre and pitch, we may be able to understand deeper patterns in animal vocalizations, and even interpret what they mean. The birds might have something to say after all. Or it might be just colorful nothing.
I also learned Arese is accomplished in multiple fields. Here is his website, where you can watch a satisfying process video of a coffee machine at work.
Anyways, here is this week’s playlist:
