What was going on when I was born?

A state appellate court ruled unanimously yesterday that a Bronx grand jury could listen to one of two tapes made by a surgeon at Montefiore Hospital and Medical Center to determine if the tape contained evidence implicating the physician in the attempted murder of his aide. The court reversed an earlier ruling by a justice of State Supreme Court in the Bronx who said both tapes were ''not relevant'' to the inquiry. Mario Merola, the Bronx District Attorney, has identified the surgeon, Dr. Richard G. Rosen, as the ''primary suspect'' in the near-fatal hammer beating of his aide, Clara Vanderbilt, on New Year's Eve. Dr. Rosen is vice chairman of the department of surgery at the north Bronx hospital.

The Food and Drug Administration asked Wyeth Laboratories today to begin an immediate, high-priority recall of a defective infant formula. Hours earlier, a company spokesman testified at a House subcommittee hearing that the company had known about the problem for possibly 10 days but had been prevented from issuing a recall by governmental procedures. The Federal agency involved later denied that that had been the case. An unknown quantity of the infant formula, sold under the brand name SMA, is deficient in an essential nutrient, vitamin B6. The Wyeth spokesman, Charles F. Hagan, testified that the problem had been caused by a worker's mishandling of vitamins.

Despite the Administration's investment tax incentives, American business is scaling back its 1982 spending plans in real terms by 1 percent from last year's level, the Commerce Department reported today. The results of the January-February survey were a disappointment to Administration officials, who count on capital investment to help bring the economy out of the recession. The survey showed that businesses expected sales to increase 9.9 percent this year, better than the 8.2 percent growth of last year. But plans for capital improvements have been cut back further from the reduction of one-half of 1 percent that was expected in the November-December survey.

One-hundred-fifty black cowboys and cowgirls from across the country - all professional rodeo competitors - will demonstrate riding and roping skills today at 11 A.M. and 8 P.M., tomorrow at 2 and 8 P.M. and Sunday at 3 P.M. at the 369th Infantry Regiment Armory, Fifth Avenue and 143d Street in Harlem. The participants in this first ''Bill Pickett Memorial African American Cowboy Circuit'' will ride bucking broncos bareback, wrestle steer, ride bulls and wild horses, and race in and around barrels. Also on the program will be a pageant on the history of black cowboys dating back to the Old West. Some of the proceeds are to be used to start an ''Urban-Western'' program for black youths and adults to teach horsemanship. Tickets are $6 to $15. Information: 293-5882. LATIN FILMS AT N.Y.U. ''Chac,'' a 1975 movie based on Mayan mythology and directed by Ronaldo Klein, is being shown tonight with English subtitles in New York University's free Spring Festival of Latin American and Caribbean Films. Offered Fridays at 6:30 P.M. in Room 703, 100 Washington Square East, the films - from Brazil, Mexico, Chile, Cuba, Colombia and the United States - include both features and documentaries. Information: 598-3395.

JOHN CAGE is still very much with us, but already he has become an icon on the landscape of our cultural life. As the unchallenged father figure of American experimental music, Mr. Cage wields an influence that extends far beyond sound alone to embrace the graphic arts, poetry, philosophy, religion and even mycology, the branch of botany that deals with fungi, in this case mushrooms, on which the composer is a foremost authority. Indeed, the entire American avantgarde would be unthinkable without Mr. Cage's music, writings and genially patriarchal personality. This year will mark Mr. Cage's 70th birthday, which falls on Sept. 15. But even now the drums are beating in anticipation of the day, and Mr. Cage finds himself jetting all over the world for celebrations of his achievements. The biggest, most ambitious and widest ranging of these festivities in New York will take place all day tomorrow - a free, 13-hour ''Wall-to-Wall John Cage and Friends'' marathon at the venturesome Symphony Space at Broadway and 95th Street (864-1414). The event will begin at 11 o'clock in the morning, end around midnight and be open to any and all, first-come, first-served. In addition, seven hours will be broadcast live, off and on throughout the day, on WNYC-FM (93.9 on the dial), and part of the program will be filmed for inclusion in a Cage documentary.

The BankAmerica Corporation's problem loans surged to $1.6 billion in 1981 from $577 million at the end of 1980, the bank holding company said yesterday in its fourth-quarter analytical report. It attributed the sharp rise to the recessionary environment. A significant part of the rise was attributed to difficulties encountered by smaller businesses, especially to those in the real estate business.