No athlete has ever been more delightful to listen to than Muhammad Ali, the big-headed, big-hearted, irreducibly quotable heavyweight boxer who elevated trash talk to an art form and who was all of 21 when Columbia Records released his spoken-word album, I Am the Greatest. He defied sports-publicity custom by ducking any effort to "handle" him. He ran his own news conferences, waxing philosophic (and rhythmic) on any topic that crossed his nimble mind — most famously, his conversion to Islam, the immorality of the U.S. war in Vietnam, and his refusal, at great cost, to take part in it.

Despite the first-person title, writer-producer-director Clare Lewins' new documentary, I Am Ali,doesn't boast any new interviews with its now-72-year-old subject, already perhaps the most-profiled figure in sports history. What distinguishes Lewins' entertaining-if-not-terribly-revelatory film from the many Ali documentaries that have come before is its focus on this most public of personalities as a friend and father.

Besides the usual (wonderful) archival footage of the champ, a softer, more private version of Ali's lilting voice is present in the form of the audio tapes he made of his conversations with those closest to him. The first time we hear that voice, it's 1979 and he's phoning his mother-in-law's house to speak to one of his seven little girls. (His eldest was 11 at the time.) The child is not pleased when her 37-year-old dad tells her he intends to fight again. You don't need to know of Ali's sad, damaging performance in his last few bouts to be moved by this. Instead of showing photos of the speakers over this exchange, or over the others she excerpts, Lewins illustrates them with electronic waveforms of the recordings, demonstrating that a voice can be at least as revealing as a face.

Along with these tapes, which Hana Ali — seventh of the champ's brood of nine, from four marriages — has made public for the first time, Lewins got access to the champ's inner circle. Ali's longtime manager, Gene Kilroy, and trainer, Angelo Dundee, sit for new interviews. His younger brother, Rahman Ali, talks about how the kid born Cassius Clay would ask him to throw rocks at his head so he could practice evading punches. Along with daughters Maryum and her half-sister Hana, we meet one of the boxer's two sons, Muhammad Ali Jr. (Yes, he was targeted by bullies in school, and no, he had no yen for fighting, the poor kid.) Ali's old foe George Foreman, whom he'd dubbed "The Mummy" in the run-up to their 1974 "Rumble in the Jungle," shows up to praise Ali as one of the finest men he ever met. NFL legend Jim Brown and Mike Tyson and even Sir Tom Jones (his presence is unusual, at least a little) are all on the guest list, piling on anecdotes and accolades.

It's never boring. Lewins keeps the space skipping along, using famous '70s R&B/soul hits from the likes of Stevie Wonder, Bill Withers and the Staple Singers to keep it bouncy. But as with most documentaries and biopics that opt to cover a life instead of a revealing sliver thereof, it's all a little too gauzy to lodge in your memory. (The best Ali documentaries of the past couple of decades — When We Were Kings, Thrilla in Manila, Facing Ali and the ESPN 30 for 30 film Muhammad and Larry — have all narrowed their focus to specific fights/eras. Even Michael Mann's frustrating 2001 biopic Ali,which starred Will Smith as the champ, confined its investigation to one decade.)

And like most documentaries made with the cooperation of the subject and/or the subject's family, it's hardly as critical as it might be. The closest it comes to suggesting the man might've had a flaw is when Veronica Porsche points out that Ali began seeing her — she was 18, he was 32 — without mentioning he was already married. She eventually became his third wife, but he wasn't faithful to her, either. It's not at all surprising that monogamy might prove difficult for one of the most famous, charismatic and extroverted men of the 20th century, but no one says anything even as gently candid as that.

What we learn is that the one-third of his children who appear in this movie say he was an involved and loving dad who saw to it that all of his kids knew one another and spent time together as one family. Kilroy even contributes an anecdote about a friendship Ali formed in the early '70s with a little boy battling leukemia. "I'm going to beat George Foreman and you're going to beat cancer," Ali kept telling the boy, but only Ali held up his end, sadly.

Since it's so close to hagiography, it's appropriate that its most unfamiliar story — to me, at least — comes when George Lois, a famous ad man who figured prominently in a recent This American Life episode, talks about how he got the idea to pose Ali as the Christian martyr St. Sebastian for a 1968 issue of Esquire published soon after he refused induction into the Army. Ali got on the phone with Elijah Muhammad to make sure it was OK for him to "dress up" — that is, affix bloody arrows to his bare chest — as a famous Christian. Elijah gave his blessing only after Ali passed the phone to Lois and the two men had a 15-minute theological teleconference. Ali lived as he believed.

One of his beliefs, expressed to explain his habit of taping his family and friends, was this: "History is so beautiful. At the time we're living in life, we don't realize it." It's the reason documentaries exist. I Am Ali'scontributions to the mountain of extant Ali scholarship are slight, but the privilege of eavesdropping on a man who inspired so many while he asks his little girl Maryum if she's yet determined her purpose on Earth is not.

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