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"For me, uncovering the composition of a genius’ work that had been lost for centuries is as thrilling as trying to uncover one of the big secrets of nature," says physicist Uwe Bergmann. (Credit: Chrysti/Flickr)

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X-rays reveal hidden notes in 200-year-old opera

Scientists blasted X-rays at a damaged musical score to reveal the musical notes hidden beneath a layer of black carbon. Now, for the first time in over 200 years, Luigi Cherubini’s most famous opera can be heard in full.

The beautifully bound 1797 opera Médée looks like an impeccably preserved relic of opera’s golden age. However, the final pages of the aria “Du trouble affreux qui me dévore” (“The terrible disorder that consumes me”) are blackened with carbon that completely obscures the closing lines.

Thick smudges black out parts of an aria from Luigi Cherubini's 1797 opera Médée.
Thick smudges black out parts of an aria from Luigi Cherubini’s 1797 opera Médée. (Credit: Uwe Bergmann / SLAC)
sheet music
By setting their sensors to look for X-ray energies associated with zinc and iron in the inks on the paper, the scientists were able to reveal the blacked-out music. (Credit: Uwe Bergmann / SLAC)

“It was amazing to be able to see the complete aria,” says physicist Uwe Bergmann, the interim director of the SLAC Linac Coherent Light Source at Stanford University, which is operated  for the US Department of Energy Office of Science. “For me, uncovering the composition of a genius’ work that had been lost for centuries is as thrilling as trying to uncover one of the big secrets of nature.”

Edited aria

Cherubini was widely considered to be one of the greatest composers of his time. Ludwig van Beethoven held him in high regard, admiring Cherubini’s ability to “weave his polyphonic virtuosity, classical stylistic polish and a truly Romantic sense of drama into music of extraordinary depth and dramatic power.”

When Cherubini first performed his operatic masterpiece Médée, the critics scoffed that it was simply too long.  It is said that in response, Cherubini simply blacked out the closing lines to make the piece shorter. For centuries, the piece was performed in its abbreviated form.

A visiting scholar from Germany heard about how SLAC scientists uncovered hidden text in Archimedes’ writings and wondered if the same process could be used to restore Médée. A few email exchanges and tests later, the musical manuscript was in a custom-built frame on its way to the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC.

Synchrotron X-rays

The synchrotron lightsource used to restore Cherubini’s opera began as a byproduct of one of the accelerators at SLAC. Electrons moving at nearly the speed of light fire off a bit of high-energy light, an X-ray, as they zip along curves in the accelerator. These X-rays are then collected, sorted and focused into a beam scientists can use to run experiments.

When this beam of intense X-rays bombards a bit of matter, such as the ink on a musical score, a few electrons in the material get knocked out of their energy orbits around the nucleus of their atoms. The holes they create get filled by electrons from a different energy orbit, and in the process secondary X-rays, called fluorescence, with exactly that energy difference, are fired off.

These excited electrons later fall down to their original, lower energy orbits and fire off the difference in energy as an X-ray.

Since the energy difference distance between orbits is unique to each element, the fluorescence X-rays coming off a material can act like an elemental fingerprint.

When Cherubini composed Médée in 1797, ink contained a large amount of metal. Cherubini’s handwritten notes were written with iron gall ink. The manuscript pages he wrote on came preprinted with the horizontal lines of the musical staff. These lines contained a high level of zinc.

By setting the sensors to look for X-ray energies associated with zinc and iron, the scientists literally had X-ray vision. The charcoal smudges—and even the paper itself—mostly contained carbon and would be almost completely transparent to the X-ray beam.

The team focused the X-ray beam down to 50 microns across—smaller than the width of a human hair. Slowly the scientists scanned the document line by line. Each side of the page took about eight hours to scan.

“It’s similar to a dot matrix printer,” says Samuel Webb, a beam line scientist at SSRL who ran the experiment. “Whenever we saw iron we would put a little digital red ink blot down, and whenever we saw zinc we’d put a little green dot down.”

Two sides of the page

The team quickly saw the hidden notes emerge on their monitor. However, they ran into a problem. The paper itself was invisible to the X-ray beam, meaning they were getting notes on both sides of the page at once during their scans.

A musical note is typically made up of a vertical stem attached to a circular head. In Cherubini’s case, the note heads consistently attached to the right side of the stems. By going through by hand and seeing which heads leaned which way, the single image of jumbled notes became two distinct pages of crisp musical notes.

“We are used to scientific experiments where you get the data and have years of work before you can make any sense of it,” says Bergmann. “In this case, we ran the project overnight and in the morning we were done. You could read the score—it was amazing.”

Source: Stanford University

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