Nineteen ninety-nine probably will be remembered as the year of excessive introspection--most reflections opening with the phrase, "As we approach the new millennium . . . "

More than any other watershed year in recent memory, this one has prompted endless musings about who we are, where we're going and where we've been.

Philharmonic Follies artistic director Anne Gentry brings a light touch to all this high-toned speculation with her comic revue of 20th-century popular music, "Oh! What a Century It Was!" The amateur production will be performed Saturday at Prince George's Community College.

Gentry's revue encompasses everything from vaudeville to the Spice Girls. The 50-member volunteer cast lip-syncs tunes by artists from Fats Waller to Elvis Presley to Madonna with short skits between the musical performances.

The cast is diverse enough to know most of the music intimately--its members range from 14 to 90 years old. Gentry recruited much of the cast from the Collington Episcopal Life Care Community, a Mitchellville retirement community, government offices and Prince George's County schools.

The Philharmonic Follies were the brainchild of Gentry, who also is manager of the Prince George's Philharmonic, an 85-member volunteer orchestra that has been performing throughout Prince George's County for 35 years.

Among the most challenging of Gentry's managerial duties is fund-raising. Until five years ago, she raised money for the orchestra by traditional means: a Valentine's Day dinner and dance, direct mail, silent auctions.

But in 1994, Gentry had an idea. She would invite supporters of the Philharmonic to perform in a comic revue in which they would lip-sync songs with a unifying theme. The money raised would be contributed to the orchestra.

"It's a lot more fun for me," Gentry says. "This is a welcome respite. It gives me an outlet for my creativity."

It's also, as it turns out, the most lucrative of all Gentry's fund-raising efforts. The Follies have gained momentum each year, drawing more and more people interested in performing in, as well as attending, the show.

"Each year it has gotten bigger because of word of mouth," Gentry says. "People really want to participate."

In past years, the show's themes have included honky-tonk, French music and tunes of the Roaring Twenties. Gentry thought it would be timely to do a comprehensive wrap this year--a history of American music during the 20th century.

Gentry researched music history to decide which artists to highlight. The fruits of her labor will be available to the audience in a 16-page pamphlet that lists the century's "100 key events" and discusses whether the music was influenced by them, or vice versa.

The recent past gets special treatment. Actors depicting the Bee Gees and John Travolta will commemorate the disco era; Patsy Cline introduces honky-tonk; and Dick Clark emcees performances on "American Bandstand" in the 1960s. Toward the production's end, one of the cast's younger members performs an original rap composition.

The sight of one's friends and neighbors whistling like Bing Crosby, hotfooting it like James Brown and thrusting like Elvis should draw plenty of laughs.

The cast "is wonderful," Gentry says. "It's a great pleasure to create something and see these wonderful people bring it to life."

The Philharmonic Follies perform "Oh! What a Century it Was!" at 8 p.m. Saturday at the Prince George's Community College Queen Anne Theater, 301 Largo Rd., Largo. Admission is $15. For more information, call 301-454-1462.

CAPTION: The Beatles, above, shown in 1965, and Billie Holiday and Frank Sinatra, both in the late 1940s, played big parts in 20th-century music, highlighted in the Philharmonic Follies revue on Saturday.