A movie documentary that uses only Lego pieces might seem an unconventional choice. When that documentary is about renowned musician-producer Pharrell Williams, it's actually sort of on-brand.

"Piece by Piece" is a bright, clever song-filled biopic that pretends it's a behind-the-scenes documentary using small plastic bricks, angles and curves to celebrate an artist known for his quirky soul. It is deep and surreal and often adorable. Is it high concept or low? Like Williams, it's a bit of both.

Director Morgan Neville — who has gotten more and more experimental exploring other celebrity lives like Fred Rogers in "Won't You Be My Neighbor?," "Roadrunner: A Film About Anthony Bourdain" and "Steve! (Martin): A Documentary in Two Pieces" — this time uses real interviews but masks them under little Lego figurines with animated faces. Call this one a documentary in a million pieces.

The filmmakers try to explain their device — "What if nothing is real? What if life is like a Lego set?" Williams says at the beginning — but it's very tenuous. Just submit and enjoy the ride of a poor kid from Virginia Beach, Virginia, who rose to dominate music and become a creative director at Louis Vuitton.

Williams, by his own admission, is a little detached, a little odd. Music triggers colors in his brain — he has synesthesia, beautifully portrayed here — and it's his forward-looking musical brain that will make him a star, first as part of the producing team The Neptunes and then as an in-demand solo producer and songwriter.

There are highs and lows and then highs again. A verse Williams wrote for "Rump Shaker" by Wreckx-N-Effect when he was making a living selling beats would lead to superstars demanding to work with him and partner Chad Hugo — Kendrick Lamar, Justin Timberlake, Snoop Dogg, Busta Rhymes, Gwen Stefani, Missy Elliott and Jay-Z. All those superstars sit for interviews and have hysterically been depicted as Lego minifigures, right down to No Doubt's Adrian Young's mohawk. (Take my money, Lego.)

We also learn something about his wife, Helen, and his anguish over being a solo artist, an opportunity he spurned when it was his for the taking. Ultimately, we learn to understand his futuristic approach to fashion and music. "What I am is a maverick," he says. No one will question him on that.

The 3D world the filmmakers have made is astonishing, with waves of clear Lego pieces washing up on a beach made of slats of Lego baseplates and Williams' collection of cool beats depicted as bouncing bricks with lights in them. There's Lego McDonald's nuggets, Lego pretzels, singing Lego fish and a Lego Anna Wintour, chilly and haughty in plastic, too.

Lego, while seemingly a restrictive medium — the hands are clips and everyone's walking is robotic since there are no Lego knees — can also, apparently, in the right hands soar, and here they do, with Williams in one gorgeous dream sequence watching the Earth's lights as a distant astronaut. It is when the filmmakers make Lego appear as water and music that are their crowning achievements. (Special kudos to the team that made Lego champagne bubbles.)

Music credits are notoriously hard to pin down — Williams claims to have created McDonald's notoriously mysterious jingle "I'm lovin' it" — and the filmmakers try to cover any misinformation with a simple disclaimer in the end credits: "Not everything in this film is 100 percent accurate. For example, Pharrell never went to space."

There are also some extraordinary moments that snap by but likely took months to make, like a Lego glimpse of the "I Have A Dream" speech by the Rev. Martin Luther King Jr. at the Lincoln Memorial and protest footage from Black Lives Matter figurines shouting "Don't shoot!"

The documentary lags a little during Williams' way up and rushes the years on top, although recreations of some of the music videos he fueled are too funny. Why he and Hugo broke up is papered over and the filmmakers struggle to find an ending, making several stutter steps.

"I think we're done," are the last words we hear as the filmmakers finally give up. But they've left behind a trippy, sweet portrait of a genius, forever in building blocks.

"Piece by Piece," a Focus Feature release in theaters now, is rated PG for language, some suggestive material and thematic elements." Running time: 93 minutes. Three stars out of four.