John Bushell was minding his own business, just pounding some boogie out of the piano on the back of his truck in Georgetown, when she appeared.

Yes, a groupie. She came like the night.

"She was around 35, I guess," Bushell recalls. "She had jewelry all over. She said, 'Are you happy doing this alone?' Then she stood there for an hour and a half and just watched.

"Finally she pulled off her hat, shook her hair loose and said, "This is what I look like. Take me with you. I'll do anything.'"

In Massachusetts, they threw quarters.

John Bushell, perhaps better known by his stage name, "Johhny B.," is learning the high price of fame. You can't take a piano out on the streets these days without being mobbed.

Especially if your voice is as bad as John B's.

"Hey, I Know I'm no Frank Sinatra."

Yesterday he parked his live-in truck broadside of Farragut Square, climbed out in his white dinner suit and black high-top Pro Keds sneakers and dug in. His stubby fingers smacking the ivories like jackhammers, he belted out a version of "Great Balls of Fire," Jerry Lee Lewis imitations and all, that sent several dozen pigeons into abrupt flight.

"Hey, don't go away. This one is for you."

After two and half months on the road, Bushell's seen it all: Radio City Music Hall, Tiffany's. You name it, he's played it. Right outside, in the truck.

"I'm saving myself for Carnegie Hall."

Only last spring he was finishing his graduate studies at the University of Boston. He played piano at the Durgin Park restaurant. Then began what he calls "The History of the Truck" (he acquired the thing from a company that repairs axle rods), accompained by photographs, which prompted him to take his awful voice and moderately good keyboard skills to school kids in Nova Scotia, Philadelphia, and across the country.

"I love kids. This is for the kids."

Bushell, 27, used to be the lowest paid elementary school teacher in San Francisco, so he claims.

But, a 38 cents a head, the school gigs don't pay for the trip, a zigzag, year-long trek across the continent and back.

So he pumps it out on the street, shoo-bop-bop-tee-booping downtown for the lunch crowds and oo-wop-tee-dooping Friday nights uptown for the bar set.

A little rag, a little boogie, a little jazz.

And what that man does to a set of shock absorbers?

Go Johnny, go, go, go!