Eric Rosser, son of an Air Force officer, was born a traveling man. "We lived everywhere," he says. "I loved it." When the time came to get his own career moving, Rosser, who had trained to be a classical pianist, couldn't imagine settling down, though he seemed to have no choice. "The concept of troubadours, who go from town to town, goes back centuries," he says. "I always envied people who traveled around with flutes. But you can't easily do that with a piano."

At least you couldn't until Rosser invented the Musicruiser. In 1982 he paid $800 for a banged-up '60s school bus, raised its roof 19 inches, moved in his 1926 Steinway grand, created a bedroom, bathroom, living room and kitchen and took his show—not to mention all his worldly goods—on the road. For part of the year, he parks in Bloomington, Ind., where he went to college and which he now calls home base. The rest of the time Rosser, 35, motors around the Midwest in his mint-green mobile concert hall, giving outdoor concerts of Chopin, Gershwin, jazz, ragtime—even rock—anywhere he chooses. He pulls over at a park or square, folds out a portable stage with green-and-purple fringe, rolls the Steinway into position and he's in business. "It's a nice, comfortable life," he says. "And it's not expensive."

Rosser attracts listeners through newspaper stories about him and by calling local radio talk shows. His take is modest. He draws mostly families and older folks, and admission costs nothing. Afterward he hawks audio-cassettes of his music, at $7 apiece, and postcards of his house-on-wheels. "On a good night I'll pull in $400 or $500," he says. He supplements that by playing concerts, nightclubs and Mississippi-riverboat cruises, but his greatest compensation seems to come from the admirers he has attracted in his wanderings. "He finds joy in just playing for the people," says Mark Sahlgren, a Kalamazoo, Mich., radio host. "He turned his back on rock 'n' roll stardom because this is in his heart."

Stardom might be stretching it, but Rosser certainly could have had a more traditional career. He studied piano for 18 years, earned a master's in classical music from Indiana University, then chucked the serious stuff for a two-year stint—on the road, of course—in John Cougar Mellencamp's band. Then he chucked that for the "freer, more compact life" of his bus.

Sometimes the pianist, who is unmarried, tops off his recitals with jam sessions in his home, which boasts a skylight over the loft bed, an antique desk and stove and a makeshift sauna. Enterprise, he points out, runs in his family. After retiring in 1973 as chairman of the Air Force Academy's political science department, his father was president of DePauw University for 10 years. His mother is a painter, and both brothers play the piano. "But not in a bus," he concedes.

From the moment he makes his entrance, crawling ceremoniously out of his living room, under the Steinway and onto the stage, Rosser has most audiences eating out of his hand. When he's done, listeners are likely to rise out of their lawn chairs to give him a standing ovation. "We can't believe someone doesn't grab him and put him in an orchestra," said retired state employee Jack Reilly after a recent Rosser visit to Kalamazoo—although his wife, Helen, admitted they really liked the crawling part best. The most heartfelt praise, however, came from steamfitter Chuck Dineen, who first heard Rosser a year ago. "That man," he said happily, "is a gas."