That was more than ten years ago.

They had no idea the instrument’s origins go all the way back to Benjamin Franklin, who developed an early version of this instrument known as the glass armonica.

Franz Mesmer, a German physician practicing in Vienna who knew Franklin, discovered hypnosis by using the sounds of the glass harp to heal his patients in the 18th century. That audiences the world over find those tones mesmerizing today is no coincidence.

“People imagine angels’ voices, like an angel’s choir,” said Anna, who previously played violin with the Baltic Philharmonic.

The glass harp fell out of fashion for about 100 years, but the couple, performing under the name GlassDuo, has brought it back to life with a repertoire ranging from arrangements of Dvořák and Chopin to Sting’s 1987 hit, Fragile. The two also perform original compositions.

At first, the Szafrańiecs’ endeavor was less a musical experiment than a physical one.

Anna and Arik Szafrańiec of GlassDuo (Photo Credit: glassharp.eu/gd_en.php)

“It was like a musical joke,” said Anna. “We didn’t treat it very seriously.”

But the more pieces they adapted to the instrument, explained Arik, who played trumpet in the same orchestra as his wife, the more they realized the instrument had great capabilities.

With almost 60 glasses placed in three rows on a table sloped so they all reach the same height, the Szafrańiecs believe theirs is the biggest glass harp in the world. Its range is close to five octaves.

Their demonstration begins after a ritual hand wash–critical before any playing session can begin.

“When you hear this,” said Arik, making his fingers squeak as he rubbed them back and forth, “that’s the sound we want for the glasses.”

The harp resembles a kind of xylophone whose notes are played on vessels ranging from deep goblets to tiny shot glasses, all of them empty. The pitch is determined by the size and grind of the glass, but Anna and Arik have to dip their fingers repeatedly in distilled water to keep them wet enough to play the rims. Finding those rapid intervals to do so without losing a beat is an added challenge.

“It seems to be easy,” said Anna laughing, “but it’s not.”

Few would suggest otherwise. Whether they’re warming up with a velvety Bach prelude or scratching out percussive sounds in Astor Piazzolla’s Libertango, GlassDuo’s fingers seem to fly at warp speed. Sometimes they cross over each other, but Arik typically plays the lower register, while Anna plays the higher notes.

“If it’s a very simple melody you can play it however you like,” said Arik, adding they have to write out more intricate passages in notation. “Then that’s the only way you can play it.”

One ethereal-sounding piano mazurka (Opus 50) by 19th century composer Karol Szymanowski, inspired by the Tatra Mountains of southern Poland, takes on celestial dimensions when played on glass.

But the duo’s pièce de résistance is their arrangement of Tchaikovsky’s Dance of the Sugar Plum Fairy from the Nutcracker Suite. Their videotaped performance of the piece has had close to two million YouTube hits.

GlassDuo has toured from Italy to India and Spain to Singapore, with more concerts planned in London, Germany and the U.S. next year.