EXPERIMENTAL MUSICAL INSTRUMENTS. VOLUME VII, #2, 12/92 PO BOX 784, NICASIO, CA 94946, USA. copyright pp.30-31 1224w

COMPOSITION: DNA TUNINGS. by Susan Alexjander.

Sometimes one is seized with an idea so intriguing that to follow it up is irresistible. A question (which actually seemed reasonable to me) appeared in 1988: if we can measure the periods of planetary orbits and translate them into sound, what about the molecular level where things are spinning and vibrating...aren't they creating sound patterns as well?...or something? Couldn't a composer write with those sounds? How are we going to hear them? I am not the first to have asked these questions, but as far as I know my partner and I, Dr. David Deamer (cell Biologist at UC Davis) were the first ones to sonically realize molecular intervals.

I'm astonished by this because it really is not difficult and is available to anybody with access to a friendly molecular biologist (with lab). Dave Deamer and I connected in 1988 and he offered to help me. I had not a shred of scientific (or computer) background and relied on him, other physicists and techno-types to guide me through. The final result was a tape, "Sequencia", for synthesizer, violin, cello, voice and tabla. The whole procedure from beginning to published tape took me two years, but knowing the process should cut months off of this time for any interested readers. Here, then, as briefly as I can describe, is the process.

Tunings for "Sequencia" came from molecular ratios of the four bases that make up the more complex DNA molecules: adenine, thymine, cytosine and guanine. Just in case anyone here has forgotten which comes first, the molecule or the atom, here's a mini review. Atoms (like carbon, hydrogen etc.) make up molecules. The atoms cluster and bond, and jiggle and vibrate. There are simple and more complex molecules...each DNA base is a simple molecule made up of four kinds of atoms (carbon, hydrogen, oxygen and nitrogen) -- the stuff of all life. The DNA double helix is a more complex molecule in its entirety. I mention this because sometimes there are references to the "resonant frequency" (however they measure it..?) of the DNA molecule, and I am sure the authors refer to this larger structure: my work was with the individual bases, and atoms.

The raw data that forms the basis for molecular music are light absorption spectra for the four bases. By "shooting" molecules of each base with light, scientists can measure which wavelengths are absorbed, or resonated in the molecule. Dr. Deamer was able to measure 18 different absorption wavelengths for adenine; 16 for guanine, 13 for thymine, and 13 for cytosine. To convert the wavelength data into frequencies, you follow the formula f=c/l, where l is the wavelength and c is the speed of light.

Now a cautionary word about this...there is a temptation when working with both the light and sonic spectrum to see the two of them as having a direct relationship; that is, D# is blue, etc. I think we must be very careful. There is a correlation from light to sound, but no one can prove that a certain light frequency is a particular pitch other than for the sake of convenience. What we can say, I think, is that a series of light intervals can correspond to a series of sonic intervals.

So now, after converting from wavelengths to frequencies, what we have are frequencies so high as to be far beyond the hearing range, which must be octavized down to be heard at all (each halving of the frequency corresponds to a drop of one octave). They were brought down thirty-six times, although thirty-two would have brought the frequencies within the audible range. (Interestingly enough, this is roughly the amount of times planetary orbits have to be sped up to be heard--it seems Hermes was right, we are standing in the middle).

To hear these pitches which are mainly microtonal I used a Mac SE computer with Editor Librarian software and a DX7IID Yamaha synthesizer. The procedure is simple: just program in the frequencies and they are sent to the synthesizer in any chosen order.

It seemed logical to work with four separate scales or pitch collections (from low to high), one for each base, and then created a keyboard of all 60 pitches together. The highest tones are associated with the lightest atoms in each molecule: hydrogen...then become sort of Es, Fs and F#s on our western scale. Oxygen, the next lightest, are Fs and F#s an octave below.

Approximately 15 pitches out of 60 fall directly on our equal temperament scale and the entire spread is about 2 and 1/2 octaves. There are octave and fifth relationships within each base...not surprising in terms of "natural" laws but the odds mathematically must be pretty high against that happening randomly. These intervals are within four cents of just, and in some cases within 2 cents. I've also found these close matches with just thirds, fourths and whole tones, or in other words, relationships to the first nine partials (including the flat 7th partial). I'm now in the process of measuring for relationships to the higher partials, just to see if any patterns emerge.

There were some interesting performance problems with "Sequencia". Since I wanted acoustic instruments as well as electronic sounds. I first found players sympathetic to the cause, then pitches for them as close to their own tuning as possible. The background tape which plays in performance allows for more of a microtonal flood of sound. I don't recommend scoring a live keyboard part for these tunings...the problems result in a gestalt-like nightmare for any accomplished player since the notes you activate on the synthesizer sound nothing like what is written on the page!

"Sequencia" features sections for each individual base as well as ensemble or tutti sections when all of them are combined. An interesting sideline here: the pitch which I chose to tune the ensemble "scale" keynote to was C# just because it fell into place as a natural aural "center" or drone tone. Later I learned that this same frequency (136.1Hz) is the Sa (or Do) of Indian tuning that is most often used, and the pitch that most tabla are tuned to.

There are lots of "so whats" here. I agree with Aristotle's pronouncement that the ear should be in charge of sound, not numbers. But the concept of the universe as song (numbers made audible) is just too tempting. It's possible to hear any molecules using this system. Dave Deamer has given me wavelengths for water, caffeine, even LSD...

One final word. In spite of all that the musicologists and acousticians tell us about our preference for low (or simple), prime-numbered ratios such as 2/3 and 3/4 (5ths and 4ths), not ONE person has ever complained about the strangeness of these tunings. In fact, the word most often used is "familiar."

Susan Alexjander teaches classes in "Sound and Consciousness" at John F. Kennedy University in Orinda, California, and does sound track design, composition and radio work in the Bay Area. She also teaches privately. The cassette tape "Sequencia" is available from Science and the Arts, PO Box 27555, Oakland, Ca 94602.