Thomas Powell Knox, 66, chief composer and arranger for the United States Marine Band for 16 years and a retired master gunnery sergeant, died of septicemia May 11 at Palmetto Baptist Medical Center in Columbia, S.C.

Mr. Knox was one of the nation's best-known contemporary arrangers of music for concert band and wind ensembles. He wrote primarily for the Marine Band, and those compositions were often played by other bands.

"He really was responsible -- both through his original compositions and through his arranging -- for creating a lot of the sound of the Marine Band," said Col. Timothy W. Foley, the band's current director. "He had a very profound influence on band music in the latter part of the 20th century."

Few Marine Band concerts are without at least one piece by Mr. Knox, and often there are several. "We'll continue to play Tom Knox as long as there's a Marine Band," Foley said.

Many, and perhaps most, Americans have heard Mr. Knox's music, which was often based on hymns, folk music and patriotic tunes. His "God of Our Fathers" -- variations on a Methodist hymn tune of that name -- was commissioned for President Ronald Reagan's first inauguration in 1981. The piece has been played at every subsequent presidential inauguration, and it closed a congressional prayer vigil service in the Capitol Rotunda the day after the Sept. 11, 2001, terrorist attacks.

Similarly, Mr. Knox's American hymn variants, "And Grace Shall Lead Me Home," was featured at a memorial concert in Oklahoma City honoring the victims of the federal building bombing there.

Mr. Knox's "Sea Songs" commemorates the 350th anniversary of the founding of Boston. It was premiered there in 1980, and has since been played by many bands around the world. Another perennial favorite is "American Pageant," commissioned for President Richard Nixon's first inauguration.

"Most important is that [his work] is played often," said Loras John Schissel, senior musicologist at the Library of Congress. "Music is dead unless it's played, and Tom's music is not dead. That's really what immortality is for musicians."

Frederick Fennell, the dean of American band music, said Knox had "a singular position among composers of wind band music in the United States."

"Tom had a style definitely of his own," Fennell said. "It was a blend of band and symphonic music. . . . He wrote the kind of music he knew would give pleasure to other people, which is not so easy to do."

The final scene of the movie "All the President's Men" contains a sample of Mr. Knox's music. As the reporters write another of The Washington Post's Watergate stories, a television above their heads shows President Nixon's second inauguration, which opened with an elaborate Knox fanfare commissioned by the president.

The Marine Band's library contains 263 Thomas Knox arrangements for concert band, brass choir, string orchestra, wind ensembles, chorus and solo voice, and dance band. He also wrote 42 original works, including a symphony for concert band.

"He had this wonderful ability to start with something very small, just a fragment of the melody or part of a chord, just enough to pique your curiosity, and then he takes his time," Schissel said. "Like a good novel, it takes a while before all the pieces come together. What makes Tom so good is that he makes it worth the wait. There's a great payoff at the end."

Mr. Knox was born in Danville, Ill. He heard the U.S. Marine Band on tour when he was a boy and decided he wanted to play in the band. He studied trumpet and cornet with Adolph Herseth, principal trumpet of the Chicago Symphony Orchestra, and attended the University of Illinois, majoring in music. He joined the Marine Band in 1961.

John Philip Sousa, the legendary Marine Band conductor, considered Illinois the best place to study concert band composition, arranging and conducting, and he willed his extensive band music library to the university's music department.

"The University of Illinois is really the birthplace of the school band movement, the college band movement," Schissel noted. Mr. Knox "had Illinois training and spent his professional career in the 'President's Own,' and for band people it just doesn't get any better than that."

Mr. Knox lived on Capitol Hill until his retirement in 1985, in a house across the street from the Marine Corps commandant's residence. At the time of his death, he was a resident of Mount Dora, Fla., and was en route to Washington on a train when he became ill and entered the hospital in South Carolina. But despite his distance from Washington, he maintained close ties with the band.

His sole survivor and brother, Richard Knox of Boston, said Mr. Knox continued to do commissioned work for the band in retirement. And although he no longer wore the band's striking concert dress uniform -- scarlet coat with gold braid, brass buttons, navy trousers with a stripe down the side -- Mr. Knox, according to his brother, was often heard saying, "Once you put on that red coat, you never really take it off."

Knox's work has been played at presidential inaugurations.