The 1969 album Then Play On, Peter Green's last with Fleetwood Mac, signaled a spiritual quest already in progress. Jan Persson/Redferns hide caption

itoggle caption Jan Persson/Redferns

Jim Hall performs with his trio and fellow guitarist Julian Lage at the 2013 Newport Jazz Festival. Adam Kissick for NPR hide caption

itoggle caption Adam Kissick for NPR

King Oliver's Creole Jazz Band in Chicago in 1923: Louis Armstrong is kneeling, from left to right behind him are Honore Dutrey, Baby Dodds, King Oliver, Lil Hardin, Bill Johnson and Johnny Dodds. Frank Driggs Collection/Getty Images hide caption

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A 16-inch lacquer disc, a format used in the 1930s, from the collection of the Library of Congress. Most of the lacquer, the part of the disc where the sound was etched, has been lost to decay. Abby Brack/Library of Congress hide caption

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Janet Feder built a career on unusual instrumental guitar playing. Her new album, Songs With Words, will feature her singing for the first time. Courtesy of the artist hide caption

itoggle caption Courtesy of the artist

Bob Dorough circa 1960. Jon Sievert/Michael Ochs Archives/Getty Images hide caption

itoggle caption Jon Sievert/Michael Ochs Archives/Getty Images