COHO! COHO! Coho!"

The capacity crowd at the Park West, Chicago's showcase rock club, took up the chant of nonsense syllables. On stage a few weeks ago, leading the cheers, was a pudgy, bespectacled disc jockey built like the Pillsbury Doughboy. He was gyrating unsteadily near the microphone, twirling a three-foot mock cocaine spoon around his neck.

Abruptly, his band broke into a pulsating disco beat. The song sounded like Rod Stewart's "Do Ya Think I'm Sexy," but the words weren't the same. My shirt is open, I never use the buttons. Though I look hip, I work for E.F. Hutton, Do ya think I'm disco, 'Cause I spend so much time blow-drying out my hair?

Roll over, Beethoven, and tell the Bee Gees the news. Antidiscomania is a national movement:

In Kansas City, KYYS deejay Max Floyd is recruiting listeners for an antidisco "Rock 'n' Roll Army." In L.A., KROQ'S Insane Daryll Wayne is burying disco albums at the beach as part of a disco funeral.

Deejays at WLPX in Milwaukee break disco records on the air every day. So do jocks in New York, Denver and Atlanta.

The leader of this bizarre crusade is Steve Dahl, 24, the roly-poly morning jock/performer at WLUP, Chicago's hottest FM rocker and commander of the 7,000-member antidisco Insane Coho Lips Army. (Hence the Coho chant -- it's the antidisco crowd's favorite, if meaningless, rallying cry.)

Dahl says his "Do Ya Think I'm Disco" 45-rpm record sold 200,000 copies nationwide in two weeks, and more than 160 radio stations around the country are playing the impish anthem.

Dahl's antidisco legions have staged raucous rallies around Chicago, invading suburban discos, pelting dancers with marshmallows and planting antidisco bumper stickers.

Sometimes the hijinks get out of hand. Dahl's July 12 Disco Demolition Night promotion at Comiskey Park, which drew the biggest crowd of the year, turned into a full-scale riot, leaving the ballpark littered with broken disco records, bottles and cherry bombs.

But the real disturbance has been Dahl's antidisco crusade, which has reached a fever pitch in many areas of the country. Chicago's L trains and tenement walls are decorated with 'Disco Sucks' slogans. In Detroit, a pair of WWWW morning jocks organized a Death to Disco Ducks (DDD) society, encouraging listeners to parade outside discos wearing white sheets.

An L.A. station is making a no-disco album of listener-submitted antidisco albums. And a Brooklyn, N.Y., organization, the Twisted Sister Fan Club, celebrated a "victory in the battle against disco" by presenting Dahl with the first annual "Disco Sucks Award."

Dahl said his self-proclaimed battle against "Disco Dystrophy" began spontaneously. "I just tapped into this tremendous energy force," the deejay said, while rehearsing with his back-up group, Teenage Radiation. "I'm just making fun of a ridiculous lifestyle."

But that was some weeks ago, and now Dahl and his associates are afraid they may have created a monster. Jesse Bullet, program director at Dahl's WLUP, said last month that "It's on the verge of being terribly out of control. It could be a really dangerous thing -- we never intended it to be this way. It's been a marvelous promotion, but we're doing everything we can to suppress it as fast as we can." And Dahl himself, in the Sept. 7 issue of Radio and Records, conceded that "I think we made our point."

Meanwhile, the same point was being made where it counts: at the record companies and the retail stores where the disco tide has begun to ebb.

For years the rock establishment ignored disco, dismissing it as a short-lived dance fad nurtured by New York City's huge ethnic population. As one influential radio consultant said, "You can't compare New York to anywhere else. It's the ultimate disco environment. No other city has such a heavy mix of blacks, gays and Puerto Ricans, who've always been the cutting edge in any dance craze."

If anything, New York's Studio 54 only reinforced disco's narrow image. It "became known for its snob appeal," complained a Chicago rock producer. "What Midwesterner thought he could ever get in there?"

"Saturday Night Fever" changed all that. In the music business, where a record is considered a huge success if it goes platinum, the "Saturday Night Fever" sound track sold 18 million copies -- so many that the record industry coined the expression "gorilla album" to commemorate its astounding sales figures. Moreover, the film legitimized disco throughout America. Suddenly major record labels -- which initially had ignored disco's impact -- frantically began forming disco divisions and signing acts.

One example of that resistance was Chrysalis Records. The company released Blondie's disco smash, "Heart of Glass," only after the group's first pair of rock singles flopped. The song outstripped Chrysalis' all-time singles sales record, selling more than 1 1/2 million copies.

Pop radio was swept up by a similar revolution. Following the lead of all-disco WKTU, which last year became New York's top-rated radio station virtually overnight, more than 75 pop stations quickly converted to a disco format.

By the end of last year, disco dominated the pop charts, at one time capturing more than 40 percent of the Billboard Hot 100. Disco singles won even more spectacular ratings, capturing eight of the 10 top slots on the charts late last year. Chic's "Le Freak" sold more than 4 million copies alone, making it the biggest-selling single in Warner/Electra/Atlantic history. At Capitol, A Taste of Honey's "Boogie Oogie Oogie" enjoyed the same status outselling the hit singles of a formidable rock roster headed by Paul McCartney, Steve Miller and Bob Seger.

But now a growing body of music industry veterans are skeptical of the glowing disco vision, pointing to the dearth of disco superstars, the revival of black pop artists such as Diana Ross and Smokey Robinson and the sagging ratings of most disco radio stations (Even WKTU has slipped significantly in recent months, now running second to a more traditional New York black music station).

Only a few disco singles are cracking Billboard's top 10 these days. And there are other signs of decline. Warners' Disco Promotion Department has just changed its name to the Dance Music Department, while Radio and Records, a key industry tip sheet, has also dropped the term "disco" from its charts and columns. Sources at Billboard and Record World, the leading industry trade publications, have confirmed that they have had extensive discussions concerning a similar switch.

"Let's just say we're beginning to experience a disco hangover," confided one veteran rock promotion man. "If a disco hit has some type of pop hook, it'll still crossover to Top-40 stations, but otherwise you're going to see rock radio making a big comeback."

It's probably too early to write off disco as a major musical force. But it is clear that many rock stations may try to exploit their audiences' growing antidisco sentiments.

In fact, many observers charge that the disco backlash is just a teen fad fueled by crafty radio programmers trying to boost their station's ratings. They point to WLUP'S ratings, which went through the roof after Dahl's crusade began.

Lee Abrams, a prominent radio consultant who handles 60 rock stations, including WLUP, has also quietly encouraged his clients to follow Dahl's lead. Earlier this summer, he sent out a memo describing Chicago's disco backlash, advising his stations to experiment with similar campaigns.

One plan -- still in the discussion stages -- calls for huge rallies around the country, heralded by a caravan of jeeps and trucks. Sponsored by the local Abrams station, the road show would feature a rock concert, emceed by Dahl or a local deejay, who would blow up disco records between performances.

"About half our stations are doing some kind of antidisco promotion," said Dwight Douglas, an associate director of the Abrams firm. "We're not exploiting anything."

"Abrams has obviously been a major influence on the antidisco movement," said an executive at Ovation, the Chicago-based record label that released Dahl's antidisco anthem. "There's an Abrams outlet in practically every major radio market. Naturally, they'd all like to emulate WLUP'S ratings. And if an antidisco campaign will do the trick, they'll try it."

Most antidisco deejays echoed that view. "Disco is taking us back to mediocrity," charged KROO's Insane Daryl Wayne. "It doesn't have any intensity or involvement." So far, Wayne's disco funerals have been placid affairs. "We don't want to encourage any violence," he said. "We just want to bring people's apathy levels up."

Other radio programmers acknowledge considerable antidisco sentiment, but have steered clear of what they term an essentially "negative" movement.

"We want to accentuate the positive," one Boston radio station manager said. "In radio, it's not healthy to stimulate your listeners' negative feelings. They might switch stations."