On a recent Sunday morning the spacious pizza outside the city's medieval town hall was live with groups of young Italian leftists singing revolutionary songs and loudly debating the sins of the leftist government that has run Bologna for the last 32 years.

Veteran Communist Party workers mingling with the crowd appeared angry and bewildered. "I never thought I would hear such things from the mouths of comrades," said a party worker.

The bearded and guitar-toting youngsters in blue jeans were part of a mass of 50,000 who had answered the call of local extremists and come to Bologna to join a swelling chorus of criticism of the city's Communist rulers.

Their three-day meeting passed peacefully, and except for some fiery slogans and harsh gestures, there was little of the violence and vandalism that have accompanied other recent Italian student demonstrations.

For the local Communists, who have an absolute majority here, the mass gathering of disapproving leftists, who in the past might themselves have joined the party, was not a joyous occasion.

Long accustomed to muted criticism from the right, mostly regarding spiraling city debts and alleged patronage, the local Communists fear the attacks by leftist students may explode what the students see as a 30-year myth.

A small, well-run city that has won high marks for an advanced system of social services, Bologna has long been used as a showcase by the Communists, who frequently organized expense-paid visits for local and foreign journalists.

Lately, however, student complaints about university conditions have undermined the city's reputation for good government.

Even more damaging to the Communists have been the repeated charges of repression, threatening the town's progressive and democratic image.

Part of a nationide trend of university protests and hostility toward the increasingly powerful Communists, the student-city conflict has assumed a greater significance in Bologna than elsewhere.

With the Communists inching their way toward an expanding role in national politics, the Bologna party's response to current problems has come under growing scrutiny since riots erupted here last March.

The party was particularly embarrassed in the summer when a group of well-known French intellectuals, including Jean Paul Sartre, accused the city of adopting repressive measures.

Set off by the fatal shooting of 25-year-old student by a military policeman, the riots led Communist Mayor Renato Zangheri to call in police reinforcements with armored vehicles.

This may have won favor with Bolognesi with private property to protect, but for the leftist students it was "non-Communist" behavior. The muzzling of an extremist radio station, a ban against loitering in the city's piazzas, and scores of arrests of leftist activists, a dozen of whom are still in jail awaiting trial, led to further protests.

Worst of all in student eyes was the mayor's charge that the riot was the result of a rightist plot.

"The mayor and his cohorts showed total disregard of our problems," said a member of an extremist movement. One city official admitted, "We were so unprepared for the explosion that we ended up acting as if broken windows were more important than a human being's death."

The official, a Socialist, said the Communists' reaction to trouble in their city had been to deny the existence of a difficult economic and social situation. Mayor Zangheri explained the outbreak as an attempt to discredit the Communists. Other party members were hostile to the students because, said Bologna's young party secretary, Renzo Imbeni, "their violence made us feel that 30 years of patient work had been wasted."

Sociologist Francesco Alberoni has another explanation for the Communists' reaction to the rebellious students.

"Bologna is the Italian Communist Party's temple," he said, "and it is not easy for them to put up with blasphemy inside St. Peter's doors."

After years of advertising the city's successful programs for day-care centers and kindergartens, home assistance to the aged, city planning and low-cost transport, the Communists clearly dislike coming under fire.

Recently the party's regional secretary, Luciano Guerzoni, admitted that Bologna, today, is really two cities one of 484,000 reasonably contended citizens who in 1975 gave the Communists their largest majority ever, and another of 60,000 frustrated and job-seeking students.

The party's tendency is to balme the national economy and some 7,000 foreign residents for both unemployment and the hig rents that 30,000 out-of-town students are forces to pay.

The central government, the party says, is responsible for the severe overcrowding at Bologna University, a state institution.

In Bologna, says one Communist "We've gone as far as possibly can alone. Any further progress with depend on profound changes in Italian Society that for now are out of aur control."

The way the students and young unemployment sett it, "The Bolognesi Communists have concentrated on winning over the Middle classes."

One leftist lawyer said, "As long as the Communists were in the opposition they defended minority rights, now that they're in the government they couldn't care less."

One of the far's principal charges against the Bologna administration has been its close cooperation with conservatives and police to limit opposition.

With 120,000 card-carrying members and over a million people enrolled in the leftist-dominated local trade federation, Communist power in Bologna, says Deputy Mayor Babriele Gherardi, "is so overwhelming that the party identifies totally with the city's institutions and tends to become oppressive."

As the last youths rolled up their sleeping bags and headed for home when the threday meeting ended late last month, city administrators breathed a sign of relief.

The quiet presence of some 7,000 police and Carabinieri had helped to keep the peace. By meeting most of the extremists" demands for sleeping space, cheap food, and meeting rooms, Mayor Zangheri sought to show that Bologna "is a city of freedom and tolerance."

Libero Gualtieri, a regional official, says the gathering of students will probably help the Communists in their future dealings with the new laft. But others made it clear that the party knows the city's problems with its disgruntled youth are far from solved.