String of Yeasts

After reading and studying the data (so far) from The Sourdough Project, a bit of it jumped out as a possible sound pallete. The growth profiles of the five most prevalent yeasts and aabs (acetic acid bacteria) measured as increasing Optical Density over a 48 hour period. Measurements were taken in 12 hour increments and recorded from 0.1 to 1.2 levels of density.

I was drawn to this data because the graphs reminded me of waveforms.

I am not at liberty to reveal the details of the data, so suffice to say that these are 5 strains of yeast. We will call them pink, blue, orange, green and neon. The pinpoints mark the 12 hour samplings of the prevalence of the strain. So at 12 hours pink grew to around .25 OD, while neon grew to .6 OD. How to represent this in sound is the next question!

My old friend, the piano keyboard, provides a familiar sonic framework. A two octave chromatic scale will represent the sound of OD growth by stretching the OD measurement scale over the two octaves. Like this:

Each OD amount covers 2 notes. D and D# represent the .1 amount, E and F are .2 and so on. This allows some wriggle room when the 12 hour sample seems to be between two numbers as is seen with pink. The growth range for pink will run from D to F and encompass 4 notes. In the case of neon, the growth range runs from D to C and encompasses 11 notes. The differences in the growth rates will be heard in the number of and duration of the steps taken within each twelve hour time frame. So far, so good!

The time frame will run in beats and measures. Since it is 48 hours of growth, one hour can equal one measure. The step patterns will run up to the highest note indicated by the OD data at that particular 12 hour marker. That makes each sampling unit 12 measures in length – seems perfect. Even better, at 4/4 time, each 12 measure sampling unit is 48 beats long! Synchronous!

Lets lay out the first 12 hours of pink and neon. Since all the yeast densities begin from .1, all the patterns will begin with D in the 3rd octave (D3). pink grows from D through D#, E, and lands on F. For this growth pattern there are 4 notes and 48 beats, so each note will be 12 beats long. The long notes and fewer steps up communicate that pink did not grow much in the first 12 hours. Neon grows from D, D#, E, F – C. For this growth pattern there are eleven notes and 48 beats. Each note is 4.36 beats in length. So the first ten notes are four beats long, and the eleventh is eight beats. The longer note at the end places emphasis on the final growth number for that 12 hour period. Faster steps further up the scale sonify neon‘s more abundant 12 hour growth period.

Looking at the graph, it is easy to hear that the growth patterns of pink and neon invert at the 12-24 hour sampling unit. Pink leaps from .25 to .7, while neon short stretches from .6 to .75. Again, note duration and number of steps will sonify these contrasts in the data.

While a sense of growth is captured by the movement up the scale, there is not yet a sense of increasing density. To get at this, I decided to sustain the top note of each 12 hour sampling unit. As example, pink’s F and neon’s C would continue softly to the end of the 48 measures. This would follow for the last note of each 12 hour cycle and will create the sense of sonic density.

Enough talk, lets have a listen!

neon 48 hour growth pattern

pink 48 hour growth pattern

These are the 48 ms versions of the patterns. So 48 4/4 measures at 120 BPM really stretches out these relationships making it harder to hear the movement of the data. Ableton Live has a function that allows me to collapse the sequence from 48 measures to 24 measures and still maintain the rhythmic integrity of the phrase. WoW! Then the phrase can collapse to 12 measures. All of these phrases will likely be a part of the Sourdough Song, but I am still deciding which version (24ms or 12ms) conveys the data more clearly. One of the researchers on the project said the longer growth articulations conveyed the anticipation the bakers feel as they wait for their starters to grow.

Here is the 12 ms version of both strains together. See if you can hear the changes described above. Listen closely for each voice – you will hear pink holding longer tones, while neon changes tone more quickly. It helps to look at the graph while you listen.

This will likely be one a motif within The Song of Sour Dough. (What do you think of separating sourdough in the title?)

 

The Sourdough Project

A major soundscape creation for 2019 is to sonify data for the Sourdough Project. The Rob Dunn Lab at NCSU, the Ben Wolfe Lab at Tufts, and the Noah Fierer Lab at the University of Colorado are collaborating to further the study of microbiomes in sourdough starters. The Sourdough Project has gathered starters from many parts of the world in order to study the bacteria and yeast interactions that create the fermenting acids and leavening gases necessary for the creation of sourdough bread.

In October 2018, the Sourdough Project Team and two artists met at the As If Center in Bakersville NC. The As If Center (Art and science In the field) is the burgeoning vision of Nancy Lowe, who is keenly interested in exploring this fertile collaborative area.The other artist was Ferne Johannssen, freshly graduated from college, and off to see what life outside of Vermont has to offer. Ferne is a visual artist/printmaker. [Interestingly, Ferne made a print on a scoby (symbiotic colony of bacteria and yeast) which grows and ferments in kombucha tea.] The purpose of our meeting was to seed an artistic and scientific direction for sharing the data from the Sourdough Project. All three labs were represented and we spent most of our time sharing information and structuring the research paper that will come from this study. Here is a description of the study from the Rob Dunn Lab website:

There are millions of kinds of bacteria and fungi on Earth. We have found several thousand species in human belly buttons alone. Yet if you mix flour and water, the community of organisms that colonize the resulting concoction is almost always composed of a small handful of organisms that are able to leaven bread, yielding a sourdough starter. How this happens is one of civilizations great mysteries, a mystery at the heart of the bread making (and, for that matter, traditional beer brewing). Yet, while bakers understand how to make starters, the underlying biology of the species in these starters remains mysterious. Starters can produce similar effects on bread (and similar flavors), despite being composed of different species, a key different ingredient. Conversely, starters composed of the same species sometimes yield different flavors. Then there is the issue of what happens to starters over time. The organisms in starters are hypothesized, by some, to stay the same over time—an old growth forest of miniatures—even if their living conditions change. Few ecosystems are so (apparently) stable. Then again, starters can change through time, sometimes suddenly. Starters are, if anything, predictably mysterious. But not for long. We aim to understand the biology underlying the differences among starters and the changes (or lack of change) in starters through time.

The last sentence of this description is what I honed in on. My current sense of how to render data as sound is that it would be most effective with data changes (or lack of) across a timeline. The other word that caught my eye is biology. What is biology? The science of living matter in all forms and phenomena, with special reference to origins, growth, structure, behavior and reproduction. The bases of biology are macromolecules (proteins, lipids, nucleic acids and carbohydrates), cells, and evolutionary changes creating phylogenic families across species. With sourdough starters, we are at the microbial layer of life. On the microbial level, diversity rules and it may have something to teach us. That is what I hope!

The Sourdough Project team had a conference call a few weeks ago, where we saw some of the data analysis of the samples, and received updates from each of the labs. Patterns are starting to emerge as the data is narrowed and focused into categorical relationships. This is the crossroads where it all comes together in the question: What do I want from this data? This most interesting question was posed our first night at As If Center, as we sat around an outdoor fire: what is your currency? what do you want from this project? I can’t remember ever having been asked that before.

The bakers who sent in samples want to know the microbiotic fingerprint of their particular starter. The scientists want to discover some new information about the ecologies of sourdough starters in general. The artists are interested in translation, transposition, representation of the discoveries found in the fingerprints. For myself, I am looking to identify a timeline and voice the bacteria-yeast exchange that is fermentation and leavening. Here is a diagram of a potential time frame:

Water + flour =

aab(acetic acid bacteria) ~ LAB (Lactic Acid Bacteria) ~ Yeasts

which give rise (the timeline but also a phase within the process)

to VOCs (Volatile Organic Compounds) aroma

To my ear this begins with the very lively interaction of the organisms that changes over time into a lighter, gaseous state. There is an alchemy that takes place and we are trying to hear and understand that.

Still looking at TRIC (Terry Riley’s In C) as a template for orchestrating interesting timbral relationships in this context. Pattern 35 is a possible frame for rise which seems to be the name of this piece. Pattern 35 jumps to a start with an eighth note run. This is the organism interaction phase. Then the mid section is where the rise happens with more space and elevation in tone. Then the aromatic texture is very open and light and unfinished.

What other sound elements might lend to this soundscape? There are likely real live sound samples to be had from this process. Another thought is what if each starter could have its own microbiome sounded out? To do this, I need to see more deeply into the data then I have to this date.

More to come…

*Photo from The Sourdough Project website