“American Masters” (8 p.m., PBS, check local listings) presents “Pete Seeger: The Power of Song,” a celebration of the singer/activist who has been collecting, singing and popularizing folk music for most of his nearly 90 years.

Fellow musicians Arlo Guthrie, Bob Dylan, Joan Baez, Bruce Springsteen, Natalie Maines and Bonnie Raitt discuss their admiration for Seeger.

The number of songs that Seeger introduced is clearly impressive, such as the civil-rights anthem “We Shall Overcome,” “Where Have All the Flowers Gone,” “If I Had a Hammer” and the African folk song that would become “The Lion Sleeps Tonight.” Seeger’s songs even hit the top of the charts, including “Goodnight, Irene” with the Weavers and the Byrd’s version of “Turn, Turn, Turn.”

This “American Masters” film makes a nice addition to earlier “Masters” profiles of Woody Guthrie and Dylan, but falls far short of those efforts. “Power of Song” is an authorized biography and has all of the limitations of official hagiography.

The film presents Seeger as a kind of secular saint. But even in the Vatican, where they know something about the saint-making business, they hire someone known as the devil’s advocate to argue against a would-be worthy’s canonization. “Power of Song” could use a dissenting voice or two.

Much is made here of Seeger’s suffering at the hands of the anti-communist blacklist in the 1940s and 1950s. But the film completely airbrushes Seeger’s political resume. The earlier “American Masters” on Woody Guthrie was much more up-front about that singer’s misgivings about his work with Seeger and their group, the Almanac Singers. In their music, recordings and benefit concerts, the Almanac Singers showed rather blind obedience to Moscow’s Communist Party line, even after Joseph Stalin made a nonaggression pact with Adolf Hitler. In that film, Guthrie makes nervous wisecracks about the dubious logic and questionable morality of their choices.

There are no wisecracks or moments of self-doubt or self-deprecation in “Power of Song.” And I’m not sure whether I’m more disappointed by its lack of honesty or its absence of humor.

Seeger is a remarkable man and venerable figure, responsible for musical and political movements and someone who helped transform the Hudson River from an open sewer into something beautiful. But a three-dimensional historical figure deserves a less one-sided biography.

In the long run, a film like “Power of Song” does its subject and the music an injustice. It’s just another glowing account among many that presents Seeger as a secular apostle for an earnest and insular folk scene where an atmosphere of self-righteous piety borders on self-parody. It also ignores why some former folkies, most notably Dylan, had to leave the music and its acolytes behind. Could it be that they found the sanctimony suffocating?

Tonight’s other highlights

¢ The top-10 women perform on “American Idol” (7 p.m., Fox).

¢ A house with three boys and no rules needs the “Supernanny” (8 p.m., ABC).

¢ “American Greed” (8 p.m., CNBC) looks into prescription-drug rip-offs.

¢ Sophie’s mother sits in on a session on “In Treatment” (8:30 p.m., HBO).

¢ A tipsy teen tantrum leads to a body in a Dumpster on “Law & Order” (9 p.m., NBC).

¢ A visitor for Marin on “Men in Trees” (9 p.m., ABC). It’s back. Did you miss it?

¢ The two-part season finale of “Project Runway” (9 p.m., Bravo) begins tonight.