Correction: A previous version of this article misspelled a style of Brazilian music. The correct spelling is choro.

Phil Mathieu played in a country and rockabilly band and performed Argentine tangos and Brazilian choro music with his own classical guitar ensemble. He championed forgotten American composers from other centuries and played their waltzes, polkas and fandangos lyrically on nylon-string guitars.

For a theater pit band, he once learned the kalimba — the thumb piano from sub-Saharan Africa.

Mr. Mathieu, perhaps one of the most protean of Washington area guitarists, took musical dexterity to extraordinary lengths. It paid off with 12 Washington Area Music Association Awards, better known as the Wammies, during his career. Nine were for best classical instrumentalist, and three were for best classical recording.

On Feb. 10, Mr. Mathieu died at Holy Cross Hospital in Silver Spring of complications from a liver ailment, said his partner of seven years, singer Ruthie Logsdon. He was 50.

Mr. Mathieu (pronounced Matthew) was one of the region’s top guitarists, said David Eisner, founder of the Institute of Musical Traditions, a Takoma Park-based nonprofit group that produces concerts and workshops. “If he were a baseball player, they’d say he was a five-tool player,” said Eisner, likening him to an athlete with all the skills needed to excel.

Guitarist Phil Mathieu. (Photo by Micheal G. Stewart)

From 1997 to 2009, Mr. Mathieu was a mainstay of Logsdon’s country and rockabilly band, Ruthie and the Wranglers. “He makes even the fastest, jaw-dropping solos look all too easy,” music critic Buzz McClain wrote in The Washington Post.

In theater work, Mr. Mathieu excelled at “doubling” — the practice of playing more than one instrument for additional pay. He doubled on mandolin, several types of guitar and even such non-string instruments as the harmonica and the kalimba.

Wranglers bassist Greg Hardin once suggested that Mr. Mathieu combine two of his favorite styles — the Argentine tango of Astor Piazzolla and the surf rock of the Ventures — in one composition. He proceeded to write and record “SurfTango.”

Beyond his technical and creative prowess, Mr. Mathieu delighted in the absurdities that often came with the job.

“He had all the skills that they never prepare you for in music school, [such as] convincing a party planner that having you stand on a table while you play is not in the best interests of the music or the event,” said Bruno Nasta, a classical violinist who worked with Mr. Mathieu.

Nasta recalled that he and Mr. Mathieu once worked together at a Christmas office party at which the two musicians were escorted from cubicle to cubicle to play 21 / 2 minutes of carols for puzzled workers.

“Every time we’re taking solos and beginning to bond as musicians, they tell us we have to stop and move on,” Nasta said.

“Phil said, ‘Why didn’t someone tell us this was a Christmas job? We could have dressed up in Santa suits.’ Well, this manager got a nervous look on his face. It turned out they had been robbed during a Halloween party by someone dressed as a clown, and this was why we were being escorted.”

Philip Joseph Mathieu was born Nov. 30, 1961, in Rockville, where he graduated from Robert E. Peary High School in 1979.

After playing electric guitar in teen bands, Mr. Mathieu studied jazz and then classical guitar, first at Montgomery College in Rockville. He received a bachelor’s degree in music from George Mason University in 1989, where he studied under guitarist Jeffrey Meyerriecks.

Meyerriecks recruited Mr. Mathieu for Charlie Byrd’s Washington Guitar Quintet in 1992 after the death of John Marlow. The quintet — all guitarists — combined classical repertoire and jazz improvisation in equal measure.

In 2006, he started his own ensemble, the Potomac Guitar Quartet, with Meyerriecks, Peter Fields and Brian Litz. The group had an unusually diverse repertoire — Brazilian choro music, surf hits by the Ventures and works by American composers from other eras, such as Stephen Foster, William Foden and Francis Johnson — most of it arranged by Mr. Mathieu.

The neglected guitar music of Foden (1860-1947) was a personal cause for Mr. Mathieu. An album of Foden’s music, “American Music for Two Guitars,” by Mr. Mathieu and Giorgia Cavallaro, earned the two guitarists a 2005 Wammie for best classical recording.

Survivors include Logsdon, of Takoma Park; his mother, Marge Mathieu of Silver Spring; a brother, Stephen Mathieu of Oak Hill; and a sister, Darlene Burris of Winston-Salem, N.C.

Mr. Mathieu played more than 200 jobs a year, many of them private bookings. It was a grueling, stressful schedule that occasionally led to mistakes — and quick saves.

Litz once received a frantic call from Mr. Mathieu, who was doing a wedding reception with a flutist. He had gone to the reception from a rehearsal and found his guitar case empty.

“I pulled up in my car, and I could hear the flute player [already] doing the prelude,” Litz said. “Phil quickly put the guitar around his neck and walked into the patio playing like a strolling musician — as though it were part of the show.”