He had been treated for prostate cancer for about 10 years, his daughter Michele Auldridge, said.

As a founding member of the Seldom Scene, the Washington, D.C.-based "newgrass" band that fused bluegrass with elements of contemporary pop and jazz, Mr. Auldridge developed a refined, lyrical approach to playing the dobro.

A resophonic (or resonating) acoustic guitar, the dobro produces sound by means of one or more spun metal cones instead of a wooden sound board. (The instrument's name is a contraction of Dopera and brothers. Dopera was the surname of the Slovak-American brothers who patented an early version of the instrument in 1928.)

Mr. Auldridge's liquid, round-toned phrasing — a departure from the more clamorous style favored by previous generations of dobrists — proved more appealing to urban audiences and to pop and country-rock performers with broad musical tastes like Linda Ronstadt, Emmylou Harris and Lyle Lovett. Mr. Auldridge appeared on many of Mr. Lovett's recordings.

"We were the next step," Mr. Auldridge said of the Seldom Scene in an interview with The Washington Post. "We liked James Taylor as much as we liked Ralph Stanley, and we attracted an audience of like-minded people. We were college-educated. We were contemporary and urban. We weren't singing about mother and log cabins, because that's not where we came from."

Michael Dennis Auldridge was born in Washington on Dec. 30, 1938. His maternal uncle, Ellsworth Cozzens, played dobro on some of Jimmie Rodgers's early recordings.

Mr. Auldridge studied guitar and banjo as a boy and picked up the dobro at 17. He appeared in clubs in the Washington area in the 1960s and joined the band Emerson and Waldron two years after graduating from the University of Maryland in 1967. In 1971 he and several other musicians formed the Seldom Scene, whose weekly performances at the Birchmere Music Hall in Alexandria, Va., enhanced the capital area's reputation as a haven for progressive bluegrass music.

Mr. Auldridge also recorded solo albums. After the Seldom Scene, he played with several other bands in recent years, including Chesapeake and the Good Deale Bluegrass Band. In 2007 the International Bluegrass Music Association presented him with a distinguished achievement award, and in 2012 the National Endowment for the Arts awarded him a National Heritage Fellowship.

Besides his daughter Michele, Mr. Auldridge is survived by his wife of 51 years, Elise; another daughter, Laura Auldridge; two brothers, Tommy and Gene; and a granddaughter.

Mr. Auldridge is credited with influencing the expansive strains of bluegrass-inflected acoustic music popularized by Gillian Welch, Alison Krauss and others. At the same time he set a new, sophisticated standard for emerging dobro players like Rob Ickes and Jerry Douglas, the featured dobro player with Ms. Krauss and her Grammy Award winning band, Union Station.

"Mike changed everything," Mr. Douglas told The Post in 2011. "He phrased differently. He was the first guy to use the dobro in a more modern way, to phrase it more like a saxophone, or some other instrument."