It was like old times - the Newport Jazz Festival before it moved from the grassy park at Newport, R.I., to the cavernous concert halls in Manhattan. But with a difference.

The 12-hour salute to the 25th anniversary of the Newport Jazz Festival that took place Saturday at the sprawling Saratoga Performing Arts Center was several times larger than any Newport event - more people and more music

About 25,000 fans, the overwhelming majority of them young, crowded into the amphitheater and surrounding area, 165 miles north of New York, to hear a variety of musical styles from more than 100 different performers. There was something for everyone: for the older jazz listener, performers such as Dexter Gordon, Dizzy Gillespie and John Lewis: for the younger fans. Flora Purim, Chick Corea and Randy & Mike Brecker.

Morrison Hansborough of Washington, who has attended every Newport Festival, said: "This is the nearest thing to Newport since the festival left Newport. The atmosphere is great - and the lines (for food and toilets) are just as long."

The tendency for many listeners was to wander in and out of the concert, depending on who they wanted to hear. Most, however, were sitting in rapt attention when producer George Wein brought on the last set, starting at almost midnight.

"We're going to make a little history," Wein smiled: Then he introduced an array of performers that would stagger a recording director's imagination. They included George Benson, Dee Dee Bridgewater, Dizzy Gillespie, Dexter Gordon, Herbie Hancock, Roy Haynes, All Jarreau, Jean-Luc Ponty, Sonny Rollins and Tony Williams.

The group immediately tore into Gillepsie's jazz classic, "Night in Tunisia," which featured a marvelous break by Gordon. His gorgeous tone shone lustrously and melodies just leaped from his horn.

A tenor battle between Gordon and Rollins was anticipated. It did not materialize. Rollins played with the ensemble and offered his own "Sunnymoon for Two," with rhythm.

When the marathon concert ended at 1:40 a.m. on Sunday (it started at noon on Saturday), most of the fans were still there, screaming and applauding for more.

But Wein brought the performances to a halt to prepare for another 12-hour concert - this time featuring big bands - last night.

Said Wein, "We plan to come here again next year. I was surprised at the turnout, but we put together a tremendous show and people wanted to see these musicians."

Although the crowd numbered 25,000, the only problems police reported were traffic jams. The atmosphere was lighthearted and gay. Fans tossed Frisbees to each other over long distances, and by nightfall they were popping firecrackers and shooting Roman candles.

The juxtaposition of musicians who are more jazz-oriented with those who are predominantly pop came off well. Gillespie was responsible for that more than anyone.

In his jocular way, the trumpeter would amble onstage periodically when someone else was performing and interject his own musical comment. While Bridgewater was delivering a torch version of "My Funny Valentine," Gillespie eased in behind her first to provide some obbligatos. Then the trumpeter and singer exchanged several exquisite improvisional statements in which they squeezed and bent notes far from how they were originally writen.

Gillespie did the same when Jarreau sang "All the Things You Are." The result was a melodically more inventive singer than what we know from Jarreau's pop concerts and records and a brilliant Gillespie solo, filled with grave notes, trills and sweeping runs.

Guitarist Benson brought the proceedings to an end with a rhythmically infectious vocal of "On Broadway." The rhythmic thrust was so strong that it attracted most of the musicians back for the finale.

There were other magical moments. Bridgewater and Corea dueted movingly on "Melody Maker." Also, she and Jarreau were joined by Andy Bey for a bluesy version of "Misty."

Although yesterday was designated as big-bands day, there was plenty of orchestra work on Saturday.

George Russel, who made a name for himself as a jazz-experimenter in the 1940s, brought in an ensemble that was as contemporary as the 1970s. The group, featuring trumpetist Stan Davis, tenor saxophonists Roger Rosenberg and Rickie Ford and singer Lee Genesis, performed a mixture of advanced pieces such as "Living Time, Event IV," and the traditional "God Bless the Child."

An orchestra was specially assembled to pay tribute to bassist-composer Charles Mingus, who suffered a stroke last year, and it featured many Mingus alumni.

Quipped one listener when he noticed bassists (Larry Ridley, George Mraz and Eddie Gomez). "It took three basses to replace Mingus."