What was going on when I was born?

When Andrew Young, Atlanta's new black Mayor, talks about his plans for running local government, he generates considerable enthusiasm in the white business establishment that had become disenchanted with Maynard Jackson, his predecessor and the city's first black Mayor. They seem impressed, for example, with Mr. Young's immediate assault on petty misconduct and street crimes in the central business district of this convention-dependent city. The enthusiasm cools, however, when the politically sophisticated Mayor talks of his long-range plans for stimulating the city's economy by turning Atlanta into a center of international trade for developing nations, with City Hall serving as the driving force behind such a move. Work at U.N. Cited It may seem like a natural move for Mr. Young, who accumulated a number of contacts and a wealth of knowledge about the needs of developing nations while a member of Congress and as United States delegate to the United Nations during the Carter Administration.

SEVERAL of the singers and musicians who will be celebrating love musically this Valentine's Day weekend gathered around the reproducing piano at the New Ballroom, 253 West 28th Street (244-3005), the other day to discuss the state of love songs. They were around that particular Knabe concert grand, an unusually subtle variant of the old player piano, because it, like them, will be celebrating love - at brunch from noon to 3 P.M. on Sunday, which is Valentine's Day. The centerpiece of the piano's program will be that compelling aphrodisiac, Ravel's ''Bolero,'' transcribed and played by Morton Gould in 1927 at the tender age of 14. Mr. Gould, who is now 68, will be at the New Ballroom Sunday to hear his piano roll played for the first time in public. The other artists who will celebrate Valentine's Day through the medium of the reproducing piano are Sergei Rachmaninoff, who will play Chopin's ''Maiden's Wish,'' Joseph Lhevinne, who will serenade the audience with Beethoven's ''Moonlight'' Sonata, Rudolf Friml, who will play his ''Firefly,'' Vincent Youmans, who will offer ''Tea for Two'' and other selections from his ''No, No, Nanette,'' and Richard Rodgers, who will play a group of his love songs - ''Without a Song,'' ''Baby's Awake Now,'' ''Yours Sincerely,'' ''You Never Say Yes'' and ''Why Can't I?''

A Police Department study tracking 3,000 felony arrests that were processed by the Manhattan District Attorney found that 51 percent were reduced to misdemeanors and concluded that a third of those reductions were not the result of legal problems. The study said that the reductions had occurred because the District Attorney's office elected not to proceed with felony prosecution for any of three basic reasons: the nature of the crime, a prior relationship between the suspect and the victim or the suspect's limited or nonexistent criminal history, The police orginally decided to monitor Manhattan felony arrests for two months last summer after District Attorney Robert M. Morgenthau complained that poor police work was hampering his prosecutors. Who is responsible for thousands of felony arrests resulting in misdemeanor charges and lesser sentences has been a nettlesome question for criminal justice agencies, which often blame one another. No Quarrel With Study In the report, which was released yesterday, Mr. Morgenthau's office acknowledged that 33.8 percent, or 1,013, of the felony arrests had been reduced to misdemeanor charges for reasons that had nothing to do with police work or the strength or weakness of the arrests.

Businesses reduced inventories by 0.4 percent in December, matching the biggest decline during the 1975 recession, new Commerce Department figures indicated. The drop was interpreted as a sign that companies were trying to break out of the current downturn. The report said sales also fell, by 0.6 percent, leaving the inventoryto-sales ratio unchanged at 1.49. (Page D1.) President Reagan said he would give Congress room to cut his 1983 budget, but that he was not ready to yield on plans to reduce income taxes and increase military spending. G.O.P. Congressional leaders told Mr. Reagan that his proposed budget could not be passed. Paul A. Volcker, Federal Reserve chairman, said that the big projected budget deficits posed a threat to the financial markets. (A1.) The Conference of Mayors joined in growing criticism of the budget proposal, saying it would ''seriously undermine the economic and social health of cities.'' (D15.)

Last Sunday, a San Francisco man told the police, he was set upon by a pit bull when the dog's owner slipped the leash and shouted, ''Kill him, kill him!'' The dog attacked, biting the man on the abdomen, arm, hand and leg and sending him to the hospital. Last week, a 2-year-old boy in suburban Pleasanton was attacked in his yard by a 60-pound pit bull that dragged the youngster along the ground until his grandmother managed to free him. Fifty stitches were required to close gashes on the boy's head and body. These and other attacks by pit bulls, dogs trained to fight other dogs in clandestine matches that draw hundreds of paying spectators and high-stakes gamblers, have caused mounting concern in California as the animals proliferate both as pets and fighters. 'A Lethal Weapon' ''The pit bull has one major characteristic,'' said Richard Avanzino, director of the San Francisco office of the American Society for the Prevention of Cruelty to Animals. ''You might call it a flaw in its personality - it shows its love by serving its master. Some of those masters are vicious, evil, sick people who train the dog to fight and kill, turn it into a lethal weapon. If we are to believe the recent report, the animal had to be trained to attack.''

The Reagan Administration, again revising its plans for deploying the new MX missile, said today that it had dropped its proposal to place the missiles on a short-term basis in silos reinforced to withstand a nuclear attack. Instead, Defense Department and White House officials said today, the first 40 MX missiles to be deployed would be placed in existing Minuteman silos that have not been reinforced by concrete and steel, or ''hardened,'' as the Administration envisioned last October. The decision not to use ''hardened'' silos on a short-term basis was made because Administration officials came to agree with Congressional critics last year that strengthening the silos ''wasn't necessarily worth the money,'' a Defense Department official said. As a result of this agreement, he said, Congress passed a measure barring use of department funds for such a system.

State taxes are usually an afterthought once the Federal return has been completed, but this year there are several important new developments that will affect residents of New York, New Jersey and Connecticut. New York, for example, has lowered the maximum tax on wage and salary income, increased the standard deduction, and created a new tax credit for solar- and wind-energy systems installed in a residence. Connecticut has enacted a new unincorporated business tax and New Jersey has added a ''use'' tax form intended to extract sales tax from people who buy merchandise out of state. For 1981, New York State lowered the maximum tax on personal service income from such sources as wages, salaries and professional fees to 10 percent of taxable income in excess of $17,000. In 1980, it was 11 percent of taxable income in excess of $15,000. The state has also increased the standard deduction, for people who do not itemize, to 17 percent of income, up from 16 percent last year. The maximum and minimum deductions have been raised by $100.

Witnesses to the fatal Stouffer's Inn fire who were hypnotized to aid their memory will be permitted to testify in the arson and murder trial, according to a ruling today in Westchester County Court. The decision, by Judge Lawrence N. Martin Jr., rejected a defense claim that the witnesses' recollections had been tainted by questioning under hypnosis. It also removed the final barrier to the start of the trial, which will begin Feb, 22 with jury selection. According to rulings in nearly three weeks of preliminary hearings,the prosecution will be able to proceed with its case virtually intact against Luis Marin, a 26-year-old coff ee waiter at the hotel in Harrison, the center of Westchester's corp orate development.

''If they like my language as much as I like their money, then we'll have an agreement.'' - Peter J. Pestillo, Ford negotiator at talks with auto union. (A17:3.)

Reacting to the death on the street last month of a homeless woman, the city is moving more quickly to get court permission to forcibly hospitalize people in immediate physical danger who refuse help. The dead woman was 60-year-old Rebecca Smith, who froze to death in a cardboard hut on 10th Avenue and 17th Street 10 days after her situation was first reported to the city's Human Resources Administration. At the time of her death, the city was pressing for a court order to help her. Since then, four people, all women, have been taken against their will to hospitals as a result of short-term protective orders obtained by the agency. In the last three weeks a total of 23 cases have been referred to the agency's lawyers, but most of them were resolved when the people eventually accepted help.

International Three missions to El Salvador have been set by Democratic members of Congress amid rising uncertainty about United States policy there. The three delegations' trips were planned separately, Congressional aides said, because they are being undertaken for different committees and offices. (Page A1, Column 2.) Thousands of Syrian troops battled insurgents in the central city of Hama for the ninth day, according to Western diplomats in Damascus. The Government again denied that fighting was taking place. (A1:3-4.)

Eddie Murphy was working New Jersey Route 3 like a ball boy at a tennis match - standing poised on the shoulder until traffic whizzed by, then pouncing onto the roadway to snatch a hubcap and darting off. Holding up the gleaming, spoked wheel cover of a Cadillac, he predicted that 1982 would be a vintage year. This is the opening of another pothole season, a time when snow and ice begin to retreat, revealing pock-marked roadways that look like they had been abandoned by highway departments and left to the Luftwaffe. Motorists throughout the metropolitan region complain that by March of each year they need lunar vehicles to negotiate the roadways.