YUMA, Ariz.-- It's winter in Yuma County, Arizona, and you're walking through a crowded street festival in mild, sunny weather.

It might be Military Appreciation Day in downtown Yuma, or Somerton's annual Tamale Festival. The streets are full of people and food smells permeate the air. At the end of the street is a stage with pulsing amplifiers, drawing in the ambling crowd like an electromagnet, arresting their aimless movement and riveting their attention to a man in Ray Ban sunglasses playing a low-slung Fender Stratocaster.

They see plastic black and teal green, but are fixated on the lyrics and the voice, testifying about Mustang Sally and pride and joy, cold shock and the mountains crumbling to the sea.

The singer playing the guitar is Tom Coz, a long-time employee of U.S. Army Yuma Proving Ground (YPG), backed by the Drifters, who include YPG employee Tab Wilcox on bass.

"We all have fun and make sure we like what we are doing," says Coz, and what they like doing most is playing the blues.

Coz, a Yuma native, first worked for YPG in the summer of 1974 while on summer break from Yuma High School. He returned for another summer stint the next year, before being hired on full time upon graduation. He spent a year working in ammo conditioning chambers before moving over to observation, tracking impacts from artillery and rocket test fires, along with airbursts from illuminating mortar rounds. Today he is the section lead--and one of the longest tenured personnel at YPG, showing the same enthusiasm for the mission throughout the decades.

"I like working with the people. The job is still a challenge, even now, and I really like that challenge."

He recalls surveying equipment from the 1950s that was still in use when he started, and marvels at the technological advancement the tools of the trade sport today.

"The way we do the job is still the same, but what we do it with is different. It is more electronic and digital now, and better adapted to what we do. It's much more advanced now."

Even back when he was working summers at YPG, Coz was already playing guitar, sneaking into the music room at Yuma High after hours to rehearse with whatever lineup his garage band had in a given week. His tastes ran toward the blues even then, though his primary fare was rock and roll.

"In high school we all have a band, but we were just messing around. We thought we were good, but it didn't really sound good."

He began playing the guitar seriously 20 years ago, upgrading his guitars and taking a student's ear to the music of guitarists he admired, from Robin Trower and Billy Gibbons to B.B. King and Carlos Santana.

"I didn't want to play them perfectly, but I wanted to pick up how they did it," he explained. "You could tell that when they played a lead or a note, it was the way they felt--it came from the heart."

There were hardships and heartbreaks along the way, from lugging heavy speakers and organs to gigs to losing a treasured white Fender Startocaster to gravity when his guitar strap snapped as he left the stage at a local eatery. But Coz remained committed to being an evangel of the blues, regardless of how unlikely a genre it was for the desert southwest.

"When I first started kind of edging toward the blues, a lot of folks said, 'you won't get many gigs.' But we did, after a while. You'd be surprised how many people in Yuma like this kind of music."

Aside from the public festivals, he has played new year's eve gigs at establishments in Yuma and Quartzsite, at the opening of music stores, and throughout the year at most of the community's best known restaurants and bars that boast live music. The band most recently played at Yuma's Air Show, the largest community event of the year.

Though he has no plans to retire from his day job, he still considers how being freed from the constraints of his demanding job would enable him to play gigs more often, and further afield than the Yuma area--there are a finite number of miles a band can travel on weekends and be back for work on Monday morning.

"Las Vegas is good, but they contract bands by the week."

But all of that is for sometime in the future. For now he is content to play to his committed fan base in Yuma, particularly with son Brandon, a music teacher at Yuma Catholic High School, on drums.

"I'm trying to get people to like the blues," he said. "There are a lot of folks who enjoy it, and I love playing it."