The harmonica, the popular, pocket-size instrument developed in the 1800s in Europe, came to the United States when a German harmonica maker sent one to immigrant relatives. From that one import grew a musical trend that became a mainstay in most styles of American music, and, as film producer Todd Slobin says, “You can’t have your TV on too long before you hear harmonica music in a commercial… about anything.”

A Houston-based employment attorney by day, Slobin joined forces with childhood friend and director Marc Lempert a few years ago to write a screenplay involving a character who played the harmonica. “We heard about a meeting of the Society for Preservation and Advancement of the Harmonica that was going to be held in Dallas and decided to go up and get some background,” Slobin said. “However, after being there for one day, the focus of our project changed completely, and we began work on a documentary about how the harmonica had changed people’s lives.”

Their documentary—Pocket Full of Soul—has taken the duo around the world, interviewing harmonica players from all musical genres and all walks of life. The result?  “A film that will be playing in theaters near you by the end of this year,” the filmmakers promise.

“The experience of making this film and meeting people everywhere has been as amazing as what we’re trying to accomplish. Almost everybody seemed to like what we’re doing because of our Texas mindset,” says Slobin, still somewhat surprised the project has taken on a life of its own.

Like Slobin, Lempert became interested in film making as a teenager. “I began cultivating my skills and, hopefully, my talent, in college, eventually earning a master’s in film directing from UCLA, but there are no filmmakers in my family.

“When I told my parents the career direction I wanted to pursue, my mom kind of freaked out because she saw into my future with school loans hanging over my head,” Lembert said. “However, once my parents saw the positive effect it was having on my life, they were thrilled.”

In making this new documentary, the filmmakers interviewed hundreds of harmonica players and fans of harmonica music, including some of the luminaries of the music world. “We never wanted to ambush any of the players we’ve featured, but we’ve also found that most celebrities surround themselves with people — gatekeepers,” said Lempert.

Musician Huey Lewis, front man for the ’80s band Huey Lewis and the News, heard of the project and volunteered to narrate the documentary.

Country-western musician Clint Black also participated, thanks to good fortune and some Texas tenacity. “Ken Hoffman, a columnist for the Houston Chronicle, had a trivia question in his column about Clint Black,” Slobin said. “We asked him to forward information about our project to Clint Black’s father, who forwarded it to his mother-in-law, and she forwarded it to Clint. Six months later, we had our interview.”

The filmmakers landed an interview with the great John Popper, lead singer of the band Blues Traveler and a stellar harmonica player, while he was rehearsing an album in Austin.

But, they’ve also met with some resistance. Like the time they tried, unsuccessfully, to schedule a meeting with Stevie Wonder, and then, as a second effort, went to the venue where he was playing. “We were in L.A. for a shoot—interviewing and filming Taylor Hicks from ‘American Idol,’” Slobin remembers. “One of the local TV stations was down at Stevie Wonder’s show, doing a live remote. We waited around until the end of the concert, but Stevie was surrounded by body guards. I tried to give an information packet to him as he was leaving, but his body guards—looking like they might kill me—asked me to leave. I left, happily.”

The two also have had less than good luck reaching high-profile players such as Bruce Willis, but they successfully reached other harmonica greats—Philip Achile, Gary Allegretto, Jimi Lee and Warren Bachman, 14-year-old phenom L. D. Miller of “America’s Got Talent” and casual-yet-serious players such as comedian and actor Robert Klein.

Their journey to learn as much about the harmonica as they could took the two to Europe, Asia and around the U.S. “I got permission to film one woman named Cynthia in northern California,” Lempert says. “She had been mauled by a bear and had lost both arms, but her brothers devised a device so she could still play her chromatic harmonica. Being able to immerse myself in her family was one of the most inspirational experiences of my career.”

“Everyone will find something they like in this film,” says Slobin. “The harmonica is about everyone. We know this because it’s taken us into hearts of such a variety people, and people have been brought into our hearts. The harmonica is a very universally human instrument, and our film shows how the harmonica has impacted the world.

“For example, every kid loves playing the harmonica,” Slobin says. “Even my two-year-old daughter. It’s very kid-friendly. But, during the two years I’ve worked on this project, no one has ever said they hadn’t held a harmonica to their lips.”

While the film is practically all self-financed and relatively inexpensive (less than $1 million) as films go, friends and strangers who heard about the project have donated airline miles and hotel rooms. The producers also admitted they’ve had to get creative to save money.

The most difficult part of making the documentary? Deciding what to use and what not to use of the more than 300 hours of footage they’ve collected, Lempert says. “At end of the day, I want everyone I’ve spoken to represented in the film,” he says. “That’s the hardest part.”

Through their Web site—pocketfullofsoulmovie.com—the two staged an original song contest featuring the harmonica, including winning entries in the movie’s soundtrack. They’re also encouraging what they call “a harmonica revolution.”

“At one time, during the 1940s and ’50s, the harmonica was one of the most popular instruments in the world,” they point out. “It was the iPod of the ’40s and had a huge impact through vaudeville and radio. Back then, they were selling 20 million harmonicas a year. That’s down to maybe a million today. Through our film and our ‘revolution,’ we want to encourage more people to buy and enjoy making harmonica music again.”