Early in “The Pleasures of Being Out of Step,” a documentary about the writer, critic and record producer Nat Hentoff that opens on Wednesday, Mr. Hentoff declares that “the Constitution and jazz are my main reasons for being.” That may seem an odd pairing to anyone unfamiliar with the man or his work, but Mr. Hentoff has nurtured those twin passions since the 1940s.

“Duke Ellington used to tell me that ‘we gave the world the freest expression ever in the arts,’ so I always thought there was a natural tie there,” Mr. Hentoff said in an interview last week at his Greenwich Village apartment. “The whole idea of the Bill of Rights and jazz,” he added, is “freedom of expression that nobody, not even the government, can squelch.”

Mr. Hentoff, who turned 89 this month, is the author of books like “Living the Bill of Rights: How to Be an Authentic American” and “The First Freedom: The Tumultuous History of Free Speech in America.” Initially, though, he built a reputation in the jazz world, interviewing artists like Charlie Parker, Miles Davis and Dizzy Gillespie and turning the writing of liner notes for albums into something approaching an art form.

When the director David L. Lewis first approached him six years ago, Mr. Hentoff was surprised anyone would want to make a film about him: “I am not exactly a household name,” he said. But Mr. Lewis, a former producer at “60 Minutes,” regarded him as an exemplary civil libertarian, and knew little about his jazz roots or that a decade ago he was the first nonmusician to be named a “jazz master” by the National Endowment for the Arts.