To some music lovers, a "pops" concert brings to mind all manner of aural poison: syrupy strings, crass dynamics, Lawrence Welk's Champagne Musicmakers churning out froth and bubbles.

Yet it doesn't have to be that way. The term "pops" is, after all, an abbreviation for popular, and what's so terrible about a nice dose of Jerome Kern, Richard Rodgers or John Philip Sousa played by a sensitive orchestra in a lush outdoor setting? Saturday evening on the West Lawn of the Capitol, an estimated crowd of 30,000 went absolutely wild as guest conductor Erich Kunzel led the National Symphony Orchestra through a torrent of show tunes, patriotic medleys, folk songs, marches and assorted musical Americana. Despite the humidity, sodden green turf and ravenous insects, listeners clapped and warbled familiar melodies, formed chorus lines and joined in impromptu hoedowns.

Kunzel, dean of the pops tradition developed by the late Arthur Fiedler and Mitch Miller (Kunzel is currently conductor of the Cincinnati Pops, Rochester Philharmonic Pops, Winnipeg Symphony and Indianapolis Symphony, and jets in for guest stints with a half-dozen major orchestras), knows just how to generate energy and precision from a group of musicians. And when he turns his peasant-shirted frame to the audience to extol the glories of American Musical Theater or American popular song, his enthusiasm provokes immediate whoops and bravos from the audience.

Saturday's program, the third of a series of free "American Festival" concerts at the Capitol, moved from the serious (well, as serious as you can be at a "pops" concert) to the lighthearted. Hosted by WGMS announcers Renee Channey and Dennis Owens, the concert opened with Victor Herbert's "American Fantasia," a me'lange of patriotic numbers that eventually had everyone on his feet and facing the Capitol flag. Next came the Washington premiere of Maryland composer Rene Varlay's "Patrick Henry," a melodramatic, drums-on-the-horizon work accompanied by Varlay's tortured reading of Henry's "Give me liberty or give me death!" speech. Rounding out this red, white and blue segment were Sousa's "Semper Fidelis," selections from Richard Rodgers' stylistically varied score for the film "Victory at Sea," and an "Armed Forces Medley" that inspired all those members of the Coast Guard, Marines and Air Force to stand up and bellow.

From that point on, Broadway and folk songs filled the air. Richard Heyman's now-schmaltzy, now-tasteful arrangements of Kern's classic music for "Show Boat" and Charles Strouse's ditzy tunes for "Annie" inspired an outbreak of sing-a-longitis. As for the "Pops Hoedown" and "America, We Salute You"--a blend of cliche'd Indian powwow music, "Home on the Range," "Turkey in the Straw," "Swing Low Sweet Chariot," "Camptown Races" and more--well, by then the sweating and stamping and reveling had grown so extreme that Kunzel and the symphony had to oblige with three equally rousing encores.