The symphonic bands of Madison and Fort Hunt high schools in Fairfax County boarded planes earlier this week, bound for the Windy City and a place among the top five high school musical groups in the country.

The two Fairfax County groups were selected from among 30,000 high school bands around the country to perform at this week's prestigious Chicago Midwest National Band and Orchestra Clinic. The bands will perform new compositions for the audience of professional conductors and musicians from across the nation.

Unlike traditional band competitions where rival orchestras engage in pitched battle to determine winners, an invitation to perform at the Chicago clinic is a victory in itself.

"To even be asked to perform is in a sense winning a contest," said ecstatic Madison conductor Jeff Bianchi. "The invitation automatically puts you in the upper percentages of the really elite high school bands."

George Etheridge, conductor of the Fort Hunt Band (which is going to Chicago for the second time in 10 years), agrees, but adds that the two musical groups have been so busy rehearsing for their respective performances that they have not had time to savor the accomplishment.

"I don't think anyone has realized the magnitude of this thing yet," said a breathless Etheridge in a telephone conversation earlier this week. "This is not just your ordinary audience out there; these will be 3,000 professional musicians.

"That makes it really staggering," he shouted over the din of flutes and clarinets warming up for one last practice before departure.

Both bands will be directed on one occasion during the five-day clinic by guest conductors. Fort Hunt will perform one number composed by Morton Gould -- who wrote the score for the television drama "Holocaust" -- with Gould conducting. Madison band members will be directed by Lt. Col. John R. Burgeois, conductor of the Washington-based U.S. Marine Band.

While the two local conductors are full of praise for their 133 student musicians, they admit that selling grapefruits and staging garage sales have been difficult ways to raise the estimated $47,000 total the trip is costing.

"The Fairfax County school system gives me $1,000 a year for my band program," says Bianchi. "That's less than 2 percent of the budget.

"There is no support for bands in the Fairfax County school system," he says flatly.

Etheridge, on the other hand, says he no longer gets angry about the lack of support for the band programs, which leaves parents and students raising funds to pay for uniform rentals, instrument pruchases and traveling expenses.

"He (Bianchi) gets $1,000? That's more than I get. I just get a few hundred," said Etheridge wryly.

When the conductors found out the school system was unwilling to contribute anything toward the trip, they approached the Board of Supervisors, which also turned down their request.

"They said they were not in the business of paying for things like this," Etheridge recalls.

School officials agree -- they are not in the business of sponsoring the hundreds of trips which bands and other school groups take each year.

"It's against policy," says George Hamel, director of school community relations. "If once we would start it, there would be no end . . . bands go everywhere -- Canada, Europe."

County officials say they also turned down the request because it would set a precedent of providing county funds for school trips.

At the end of October a local jean store -- Zippers -- came to the rescue, providing $1 to the bands for every $10 purchase in a Zippers store.

Zippers president Robert Burke said earlier this week his store had raised close to $15,000 for the bands.

In addition, Fort Hunt students designed a "Rent a Kid" program that provided teen-agers for odd jobs. The teen-agers turned their earnings over to the band. A group of girls at Fort Hunt added more money to the fund by working in inventory at area shopping centers and giving their pay to the band.

"It's sort of sad that you have to do all this," said Etheridge wistfully. "But what can I say? These kids are great!"