Garth Knox was born to play the viola. As a youngster, he already had two sisters who played violin and a brother who played cello. "So for the family string quartet," Knox says, "it was very clear from the start which instrument I would play."

On his new album, Saltarello, Knox traverses almost 1,000 years of music history, playing not only the viola but also the medieval fiddle and the viola d'amore, a forgotten member of the viola family with an extra set of strings vibrating underneath the fingerboard. Knox says the instrument appeared and then disappeared in musical history.

"A lot of babies were thrown out with the bath water," he says in an interview with All Things Considered host Robert Siegel. "And I thought the viola d'amore was a particularly big baby that had been thrown away by mistake. I and others are trying to bring it back and show just how beautiful it can be."

The instrument appears in the album's opening track — "Black Brittany," an arrangement of a traditional Irish song — and in a stripped-down version of a Vivaldi concerto. Instead of the standard orchestral accompaniment, Knox arranged the work for just two instruments: the viola d'amore and a cello.

"I noticed over the years that baroque players like to lighten things up and make it clearer by reducing the number of people playing," Knox says. "And I thought it would be nice just to see how far I could go, and in this Vivaldi piece I think we've reached the limit. I think it gains something. I think it's exciting to hear it played like this."

The oldest music on Saltarello is by the 12th century abbess and composer Hildegard von Bingen; Knox plays it on the medieval fiddle, an instrument that he says looks like what you see depicted in Renaissance paintings.

"You usually see angels playing them," Knox says. "They usually have five strings, and their bridge is flat and you can play all the strings all the time, which is the idea. It's a very beautiful instrument, and it has a very earthy sound."

Immediately following the ancient sounds, Knox jumps more than 900 years to a new piece, Vent Nocturne (Dark Mirrors), written for him by Kaija Saariaho. It's all part of Knox's musical journey.

"I thought it would be very interesting to put things together which normally you don't hear together," Knox says, "and see just what the differences are."

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