TOM DOWD beams like a silver fox behind that shaggy beard. All the time. There's good reason for the permanent smile. Music producer, recording engineer and general studio daddy to a virtual heavenful of stars from Ray Charles to the Allman Brothers, he has engineered more magic moments than Beatles producer George Martin and, heck, maybe even Phil Spector.

"Tom Dowd & the Language of Music" shows firsthand the appreciation and warmth from the musicians who worked with him. In mid-interview with "Dowd" director Mark Moormann, for instance, Ray Charles stands up and flips out when he realizes Dowd has entered the backstage. They hug, then talk old times. Charles laughs, roars, cackles. His arms fly in the air, as he remembers. That interview with the director is forgotten.

What Charles and hundreds of other recording artists know is that Dowd (much of his career in his Criteria sound studio in Miami) gave them the freedom to do what they wanted. Better than that, he introduced them to the idea of further freedom, with new things like eight tracks of tape -- a radical concept in the early days when most people worked with three or less. He helped pioneer the mixing of sounds. He brought the sound of the bass way up. Songs with new bottoms! With inspired microphone placement and a ceaseless desire to find the best overall sound, he could make a band seem like they were in the room. He worked the technology so the artists could be themselves, maybe even raise their own bar.

Dowd passed away in 2002, so music doesn't have him around anymore. But as recently as 2002, the film shows him at work still, working with a young, virtually unknown guitarist. Maybe he's seen and heard it all, but Dowd, dressed in garish tropical shirts, is always fascinated. Always working and wondering what new thing he can bring to the music.

There's appreciation, too, from Gregg Allman and Dickey Betts; Les Paul and producer Phil Ramone; Atlantic Records founder Ahmet Ertegun, whose legendary label owed untold debt to Dowd's engineering acumen; surviving members of Lynyrd Skynyrd; and Eric Clapton, who remembers Dowd's behind-the-scenes work on arguably the greatest song of Clapton's career: "Layla."

Even more numerous are the ones who appreciated him but who couldn't be here to tell us so, in some cases because they passed on. We're talking about Charles Mingus, John Coltrane, Aretha Franklin, Dizzy Gillespie, Bobby Darin, the Drifters, Otis Redding, Booker T. & the MG's, and so on. This movie shows us enjoyable footage of many of those artists, performing the music that we thought came exclusively from their throats to our ears. What we realize is that Dowd was twiddling the mixing board knobs, working those mikes, making those songs sound how they do. It was their art, but somewhere at the bottom of it all, somewhere in the deep ether of those songs and tunes, was his autograph.

Dowd, we learn, wasn't in this business from the get-go. He started as a physics geek at Columbia University and found himself part of the Manhattan Project at age 16. When he saw where his research was going, the destruction of so many people, he quit that line of endeavor. He joined the sound recording industry and never looked back. When Ertegun's Atlantic Records took him on as a permanent house engineer in New York City, his destiny was set. He recorded jazz artists like Gillespie and Ornette Coleman, and he was part of the movement that would be known as "rhythm and blues," a label invented by another Atlantic colleague, producer Jerry Wexler. Dowd would be an integral part of the southern rock sound, working for the Allmans and Skynyrd. And a whole lot of big names in between.

In the most fascinating moment, Dowd takes us back, individual track by track, over the building blocks that became "Layla," including the inspired lead runs of the note-bending Clapton and the bottleneck slide-oriented Duane Allman. It's a remarkable song; we knew that. Dowd shows us in even greater detail just why it's so. And it makes a great closer.

TOM DOWD & THE LANGUAGE OF MUSIC (Unrated, 90 minutes) -- Contains nothing objectionable. At Visions Bar Noir.

Tom Dowd, renowned recording engineer and producer, died in 2002.