Philly's Questlove and Christian McBride help paint a portrait of the artists in HBO's James Brown bio

FEATURE FILMS are often accompanied these days by a companion documentary that's spoon-fed first to an HBO or Showtime - a marketing ploy to get folks excited about the movie.

Clearly, Alex Gibney's two-hours-short documentary, "Mr. Dynamite: The Rise of James Brown," debuting tonight at 9 on HBO, was made in the same time frame as the recent James Brown biopic "Get On Up." But Mick Jagger, producer of both projects (and a lifelong fan of Brown) opted to hold back the doc, first dishing the dramatized version (with Chadwick Boseman as Soul Brother No. 1) in early August - for a now-very-clear reason.

With a personality as large as Brown's - one of the leading showmen and innovators in modern music and also a significant force in the civil-rights movement - there ain't nothing like the real thing, baby.

Had it lit up first, "Mr. Dynamite" would have blown away chances for "Get On Up" to score at the box office. As it was (and as with most labor-of-love music bio-pics), this example still did just OK.

Gibney is one of the busiest and best documentarians, and, like the biopic, his portrait also starts, contextually, with Brown's horrendous, hardscrabble youth.

Fans already know the tale: abandoned early by his parents in rural Georgia, reduced to living in and pulling johns to his aunt's whorehouse, shining shoes in front of a radio station (that he'd one day buy), discovering his innate singing and buck-dancing skills, and making a fortuitous, postprison hook-up with gospel singer Bobby Byrd.

But, while "Get On Up" put emphasis on a psychological portrait of a very difficult guy, Gibney mostly sidesteps that, choosing instead to showcase how the song-and-dance man could whip up a musical storm on stages, TV shows and in the recording studio.

It's left to his still-surviving sidekicks and fans - including musicians like Maceo Parker and Bootsy Collins, and Philly-spawned disciples Christian McBride and Ahmir "Questlove" Thompson - to explain Brown's persona and grand excesses, and to paint the big picture.

Stuff to learn:

* Brown mastered his scream technique when pretending to be Little Richard on a short impostor tour.

* Professional wrestler Gorgeous George was the role model for Brown's signature stage routine, in which MC Danny Ray - still so cute - would drape a cape over the man when he was seemingly down and out.

* When drummer Clyde Stubblefield joined the group, there were already four other percussionists sharing the stage. He vowed most wouldn't last long!

Unlike the director's recent "Finding Fela" doc, which came up short on Fela Kuti film clips, there's a treasure trove of concert and TV performances to enjoy here from the "hardest working man in show business" - juicy, meat-and-potatoes moments that demonstrate his knockdown, drag-out soul-rasping power, his amazing, slip-sliding dance moves (clearly inspiration for Michael Jackson and Prince), and his groove-centric, riff-repeating, brass-rattling synthesis of R&B, gospel and jazz.

In other words, the stuff that would spark the funk revolution and be sampled to death by the hip-hop crowd, as Questlove and Chuck D likewise testify.

Also unearthed are a few choice visions of Brown energizing the black-power movement: reasoning with a Boston concert crowd agitated by Martin Luther King Jr.'s assassination, pressing President Nixon to honor MLK's birthday, reaming out stuffed-shirt David Susskind on Mike Douglas' Philly-based variety show.

It was an attitude that also sparked anthems like "Say It Loud - I'm Black and I'm Proud" and focused future leaders like the Rev. Al Sharpton, who first met Brown at age 17 and long considered him "a father figure."

Online: ph.ly/Tech