"Cut out that noise, Cohen!" seemed to be about all his colleagues ever said to him. Tapping out Latin rhythms on the water cooler, testing every stationary object in the office for its percussive potential, Martin Cohen was not the firm's—any firm's—most popular young mechanical engineer. He admits to losing four jobs for "acting weird." On the fifth, in 1965, Martin took out an instrument he had devised called a vibra-slap and sent a loud, snakelike rattle through the office. "What the hell was that?" the chief engineer roared. It was Cohen's declaration of independence. Quitting, he launched Latin Percussion, Inc., now a $3 million-a-year rhythm instrument manufacturer and the undisputed leader in its field.

Cohen, 41, imports a variety of bells, castanets and gourd instruments from South America and Africa. But his reputation is based on his modernization of the classic drums of Latin music—the bongo, conga and timbale—and on his two patented inventions, the vibra-slap and the cabasa, which produces a variety of shuffling-grating sounds.

Both are now ubiquitous in U.S. recording studios, sound stages and concert halls. His drums carry the endorsement of Earth, Wind & Fire, Dizzy Gillespie, star studio percussionist Ralph MacDonald, Donna Summer's rhythm man Bob Conti and Latin stalwarts like Willie Bobo, Patato Valdez and Tito Puente. "Martin was the pioneer after the Cuban embargo cut off supplies of traditional instruments," says Puente. "You can really send a message on Martin's drums."

That a Nice Jewish Boy from the Bronx should have become the conga king is odd, Cohen agrees, but also slightly misleading. "I was never nice," he says. His father, who cut furs in the garment center, "used to ask me, 'Why do you have to be so different?' I had wanderlust; I'd hitchhike all over just to see what was happening." At City College of New York he married a psychology major named Marilyn Epler and the two discovered music. "We never had a phonograph growing up," he explains. "So when Marilyn and I heard José Mangual Sr. at Birdland, it was magical. His bongos flew over the orchestra, decorating it. I've been hooked ever since."

Neither Cohen nor the instruments he began to experiment with were instantly accepted. "Jews were an oddity in Latin dance halls," he admits. "My first bongos were like two rotten flowerpots, and the musicians would twist my name, calling me maricón—which is slang for homosexual. I was so intent on getting across, I let it pass right by me."

Moving to a modest house in Maywood, N.J. in 1963, the Cohens launched their cottage industry while Martin was still working as an engineer. "There were bongo shells drying all over the backyard all summer," Marilyn remembers. They risked it full-time starting in 1965 and, while raising two young children, plowed every available cent into the business. "I'd have a baby in one arm," says Marilyn, "and be taking orders over the phone with the other." By 1969 they were big enough to open a small factory in nearby Palisades Park. This year LP expanded again and now has three plants in the Meadowlands vicinity of New Jersey and a staff of 35.

The Cohens' standard of living has, not suprisingly, picked up as well. As president, Martin earns well over $100,000 a year. Marilyn, 40, the vice-president, describes the family's sprawling ranch house in suburban Hillsdale as "a self-contained entertainment center" with five stereo systems, video equipment, a $200,000 recording studio and a darkroom and photo studio. "It's easy," she says, "to stay in there for weeks if we're not careful." Last summer the family slipped away for a month on its 40-foot trawler (Conga, naturally). While daughter Andrea, 13, stays close to her mother, Wayne, 15, a budding photographer and recording whiz, is emerging as papa's heir apparent.

Wayne will need more than technical mastery to replace his father. Though not a musician himself, Cohen is in awe of them and acts instantly on their tiniest complaints. "That's what's made his products the best," says Ricardo Marrero, LP's head of quality control and artist relations. "But it's also Martin's weakness. People take advantage of him." Shrugs Cohen: "The music's an affair of the heart with me. I took Patato on a concert tour of Japan last year and he drove me crazy. When we got back I literally wanted to kill him. Then I listened to the tapes, and it all melted away."