On a hot, humid night last week, Ella Fitzgerald fans started lining up at the gates of Wolf Trap Farm Park so early that the jazz singer was still in rehearsal, her big voice rolling over the hills of Wolf Trap all the way down to the entrance on Trap Road.

The fans came for Fitzgerald, and she for them, but Fitzgerald also came for the Fairfax Symphony, which made its season debut last Thursday at Wolf Trap. Despite the symphony's growing reputation, it had previously played Wolf Trap only on "Fairfax Family Night," a free showcase for local talent.

"We've long had a desire to play Wolf Trap -- it's such a thrilling place to be. We wanted to represent Northern Virginia at that fabulous location," said manager Barbara Serage. What was missing, Serage said, was "the right formula."

The symphony found the formula's vital ingredient in Fitzgerald a little more than a year ago, when music director and conductor William Hudson went to Richmond to collect a Governor's Award for the Arts for the symphony he has guided from obscurity to professional status in the past 15 years. Another award recipient was Fitzgerald, who was seated next to Hudson.

"We're both from the same home town -- Newport News, Va.," said Hudson. "She said she would love to have a chance to sing with my orchestra sometime, and I said we would try to work it out," Hudson said.

So when the symphony and Wolf Trap began tossing around ideas for a concert, Hudson suggested Fitzgerald as soloist, and the symphony landed a spot on the schedule. "We thought that would be a good show," Wolf Trap spokesman Matt Hessburg said.

Fitzgerald flew in from her California home to perform, and perform she did. For two hours, the 68-year-old entertainer belted, growled, whispered and scatted her way through standards such as "Ain't Misbehavin'," "Let's Do It" and "Satin Doll." She brought along the Paul Smith Trio (Smith on piano, Silver Spring native Keter Betts on bass, and Gregg Field on drums), and she sang several numbers with only the trio playing."I'm thrilled to be here. I've never played here with a symphony. This is a big one," Fitzgerald said of the 106-member Fairfax Symphony, which started off the evening with a warmly received program of Gershwin, Berlin and Williams.

Fitzgerald is no stranger to Wolf Trap -- Thursday's show marked her sixth appearance there. "I'm thrilled to be here. I've never played here with a symphony. This is a big one," she said of the 106-member Fairfax Symphony, which started off the evening with a warmly received program of Gershwin, Berlin and Williams.

Nor is she a stranger to Washington, which she said "has always been a great music town. We played the Howard Theatre" in the 1950s, she said, referring to the first legitimate theater in the United States built for blacks, a Washington landmark where musicians such as Pearl Bailey and Billy Eckstine got their starts.

"I'd really like to see the Howard Theatre open up again," said Fitzgerald. The theatre has fallen into disrepair since the 1960s. "It was almost like an education. The songs I did here became popular, and that made me popular. I've got so many friends here; it was almost like home at one time."

Fitzgerald has been supplementing her trio and big-band performances with symphony shows for about 20 years, since the late Arthur Fiedler invited her to sing with his orchestra.

For about 36 weeks a year, Fitzgerald and her band perform in clubs, in auditoriums and at festivals around the country. She has been singing professionally since age 16, joining Chick Webb's band after the drummer agreed to be her guardian. But although her schedule has slowed down enough for her to "know what's in my house," Fitzgerald has no intention of stopping. "I like to feel as long as people want to hear me, I'll be there," she said.

"I'd feel embarrassed if I got out there and felt my voice was going. I'd let it go. That's what's so beautiful nowadays -- you have the chance to keep going. I don't crochet, I don't knit. I love to sing. I love people. That's just me."

Rehearsing with Fitzgerald last Thursday before the show was a thrill for Fairfax Symphony members. "She's so full of life," said Mickey Zimmerman, a first violinist who has been with the symphony since it began in 1957.

"It's fun to work with a celebrity," said clarinetist and 11-year symphony member Mary Swift.

Karen Thornton, who has been playing French horn with the symphony for six years, noted that "the Kennedy Center, Constitution Hall and Wolf Trap are showcases for the best artists in the world."

"This orchestra is unique in Washington," added Thornton. "All of us are here for the love of music and playing great music. When you finish a concert, you feel so full of joy, you feel sorry for the nine-to-fivers."