Sitting on cushions in a Tehran apartment, the guests listened raptly to the notes of the traditional Persian stringed instrument and the warble of one of Iran's premier male singers of the old school.

Then the singer and musician struck up a new tune, a ballad they had recently composed that was scathingly derisive of the mullahs who make up Iran's new ruling class. Glasses of contraband whiskey, gin and vodka were liberally refilled and the guests sang along heartily, venting the pent-up resistance and frustration of what may be the world's best-dressed subculture.

Sitting on the floor and singing the ballad's refrain were men in expensively cut suits and women decked out in costly Paris fashions -- some too daring to be worn on the Champs Elysees, much less the streets of the capital of the Islamic Republic. One woman, heavily made up and her hair dyed blonde, wore a sheer blouse made only slightly less transparent by some strategically placed black lace.

A little more than a year after Iran's Islamic revolution, the mullahs can claim victory over a political challenge by Western-oriented liberals, but they have yet to win the battle of the boutique. Try as they may, the new powers that be have proved unable to eradicate a stubborn strain of Western influence -- some would say decadence -- that infects the Iranian upper crust.

"I would like to personally hang all these mullahs," one guest whispered as he listened to the ballad, a tale of a simple country mullah's rise to riches and fame under the new government. Another guest openly expressed the hope that the government would be overthrown in a military coup. A third spoke nostalgically of the days before the revolution, referring to the deposed shah Mohammad Reza Pahlavi as "His Majesty."

Among the guests on the recent evening in the spacious Tehran apartment were a former bodyguard of the deposed shah, a senior military officer of the old imperial armed forces, a former gambling entrepreneur, a high official in one of the current government's ministries, a television news announcer, the owner of a fashionable dress shop and several leading businessmen.

They are among the few surviving members of Tehran's once flourishing cocktail and party circuit. Some of their friends have been executed or jailed, many have left the country and others have seen their property confiscated in the name of the Islamic revolution.

Many other Iranian also are dissatisfied with the new government and the Islamic restrictions it has tried to impose. However, the party guests and their upper class friends seem even less inclined than their increasingly reticent compatriots further down the social scale to publicly demonstrate their opposition to the government. Instead, they generally prefer to continue trying to work within the system.

It is only on occasion that they gather late at night to play the role of a high society underground, then stealthily glide away again before dawn in their Mercedes and their Jaguars.

"What's new?" a newly arrived visitor asked an Iranian friend recently.

"Oh, not much," came the laconic reply. "The mullahs have grown fatter. And their wives are wearing more expensive jewelry."

Indeed, since the revolution there seem to have been few radical changes in the way most Iranians live. As far as Tehran is concerned, the changes have been subtle ones -- a succession of developments that have tended to augment and extend the authority of the Shiite Moslem clergy. The result has been that since the Islamic Republic was officially proclaimed by Ayatollah Ruhollah Khomeini 13 months ago, more emphasis has been put on Islamic than republic.

The Iranian capital still looks much the way it did in the months preceding the February 1979 revolution. Construction cranes still stand idle all over the city and half-finished buildings loom as monuments to the turbulence that preceded the overthrow of the shah's monarchy. Tehran looks like a boom town caught in suspended animation.

Despite talk of Islamic dress code and the clergy's campaign against Western influence, people's appearances do not seem to have changed much either. Contrary to the impression given by the legion of chador-clad women who periodically march across American television screens, roughly half the women in the capital continue to wear Western-style clothing -- sometimes outrageously so as a protest against the Islamic regime. Generally however, the two styles mix easily; it is not unusual to see women in the black head-to-toe veils walking side by side with woman in Western garb.

Nor has the revolution had any appreciable effect on Tehran's nightmarish traffic jams, which choke the city with a thick smog. The only noticeable change is that traffic signals, regarded by drivers as more or less optional before the revolution, have become even more so.

This disregard for rules and regulations can also be seen in the rows of motley stalls that now line a number of Tehran's main avenues. Shopkeepers are less than happy to see the tents and shacks spring up on the sidewalks opposite their display windows.

A walk down Mossadegh Avenue, formerly Pahlavi Avenue, now means running a gauntlet between the established shops and the jerry-built stalls. Shoppers can be seen picking over tables piled with imported clothing, browsing through Marxist literature, looking at color posters of such disparate characters as Ayatollah Khomeini and John Travolta or selecting locally made bootleg cassette tapes -- sometimes with a Donna Summer disco number blaring over a loud-speaker.

Spearheading the fight to cleanse the Islamic Republic of the influence of taghouti -- a word Khomeini took from the Koran that literally means "the idol worshippers" -- has been the Center for the Abolition of Sin.

One of several Islamic revolutionary organizations that have been spawned in the past year, the center has emerged victorious in a scrap with Foreign Minister Sadegh Ghotbzadeh, who challenged its legality.

Working under the aegis of Iran's Islamic revolutionary prosecutor general, the center has taken on such burning social issues as the employment of male hairdressers in women's beauty salons and the holding of "mixed" marriage ceremonies.

In a recent statement, the center said its investigators had been shocked to find out that "those affiliated to the taghouti [the shah's] regime . . . still carry on doing women's and girls' hair." It added: "Male hairdressers' salons have been put at the disposal of loose women and girls and serve as hangouts for them to meet pleasure-seeking men." The center ordered all male hairdressers to stick to their own sex or face the closure of their shops.

The center also decreed that men and women must not congregate at wedding ceremonies or listen to "banal music" played by bands or tape recorders. "Male and female ceremonies must be held separately -- that is, men and women should celebrate in separate halls," the center's statement said. "We are not opposed to happiness and joy in wedding ceremonies, but according to Islamic tenets neither women must entertain men nor should men entertain women."

To show it meant business, the center announced that its investigators had closed down five restaurants and turned their managers over to the revolutionary courts.

Nor have the practices of "health and leisure clubs" escaped the vigilance of the center's agents.

"According to information we have received, huge gambling on billiards, table tennis and table football is carried out at these places," the statement said. "Moreover, at such places our youths are initiated into moral and social corruption. Cases have been seen of youths smoking narcotic-filled cigarettes most impetuously."

The center's greatest achievement in the battle against sin was bulldozing of Tehran's red light district in March. But since then, the capital's homeless but dedicated prostitutes have made something of a comeback. A number of them have installed themselves in tents in one of the city's main parks.

If there is any common thread through the different political and social groups competing for power in revolutionary Iran, it is probably a fundamental anti-Americanism -- an opposition, friendly Iranians are quick to point out, to the U.S. government, not the people.

The United States is used as a scapegoat for just about anything that goes wrong and the guiding philosophy of the revolution might be stated: "When in doubt, blame it on the Americans."

But even Iranians normally inclined to give the Tehran government's anti-American line the benefit of the doubt were taken aback by this headline recently in the newspaper Islamic Republic: American Mercenaries Kill 263 Cows."

The story in the organ of the powerful Islamic Republican Party went on to explain that 85 cows had died and another 178 were near death because of water contamination in the pastures of the Nowruzabad Agro Co.

"Haji Safar Ali Nejad, head of the Islamic Society of Cattle Breeders, said pregnant cows in one of the company's pens fell one by one," the story said. Informed of the incident, the chief of Tehran's central revolutionary committee, said he suspected foul play.

"At this crucial period our country is passing through, only counter-revolutionaries and associates of American imperialism could have wanted to deliver such a blow to the Islamic revolution," he was quoted as saying.

The committee chief, identified only as a Mr. Alizadeh, said that two former workers at the company had been arrested in the case. He predicted, however, that "the real culprits will be found soon."