November 19, 1982

The International Harvester Company, which recently avoided default by negotiating an agreement with its lenders, said failure to reverse its declining sales in the next few months could force it to file a bankruptcy petition. Harvester acknowledged in a statement filed this week with the Securities and Exchange Commission that it had been losing its customary share of the truck and farm tractor markets, both severely depressed. It said its survival depended on ''significant'' improvements in these markets.

Seen from this Iraqi border command post 170 miles southeast of Baghdad, the front was mostly quiet. A small wood that was said to shelter Iranian troops two and a half miles away could be seen through field glasses. There had been some sporadic fighting to the north in the morning, and an occasional shell was still being fired by Iraqi gunners. There was no reply from the Iranians, who, according to Iraqi officers, were short of ammunition.

President Reagan was told that the G.O.P. lacks the votes in the House to advance the 1983 tax cut by six months. Congressional leaders said they expect Congress to demand cuts in the proposed arms budget and to reject further cuts in social programs. (Page A1.) Martin S. Feldstein, Mr. Reagan's chief economic adviser, told him that a highway repair plan urged as a way to create jobs might actually cost jobs. (D16.) Leaders of the steelworkers have approved major concessions, including a $2.25 an hour cut in wages and benefits, according to union and company sources. In return, they said, the companies have offered workers a share in their profits. Locals vote today on the plan. (A1.) The U.A.W. and Chrysler will resume talks soon in the dispute that led to a strike in Canada. (D16.)

Argentina's central bank, in a major restructuring of part of the nation's crushing foreign debt, announced today that it was substituting five-year bonds and promissory notes for $4.7 billion in debt that private concerns must repay foreign creditors over the next six months. The central bank declared that it would not begin paying back the principal on the bonds and notes until the fifth year. It said, however, that it would pay interest every six months. The move, in effect, means the private debtors will repay the principal owed to foreign banks with Government bonds rather than with cash. The dollar-denominated bonds will only be negotiable abroad.

IT would seem a normal weekend in New York's musical heartland. Tonight, the Sylvan Wind Quintet is playing Ravel and Rossini and the Wond'rous Machine is singing ensemble music by Byrd, Lassus and Palestrina. Tomorrow in Brooklyn, there's Boito's opera ''Mefistofele'' and not far away a 40-piece orchestra playing Haydn and Mozart. Sunday, Lynne Aspnes plays her harp on Manhattan's Upper West Side and not far from there the Bach series called ''Evenings With Johann S.'' continues. Typical events, certainly, except for one thing - all of them are taking place in churches. Places of worship are bulging with music, much of it secular. It is a symbiotic coming together - where the aspirations of musicians, many young and in need, meet the aspirations of New York's churches. The Sylvan Wind is playing at St. Peter's Lutheran Church - known also for its jazz -in the Citicorp Center, Lexington Avenue and 54th Street, at 8 tonight. At the same time the Wond'rous Machine is singing in St. Ignatius's Episcopal Church, West End Avenue and 87th Street. ''Mefistofele,'' which is also part of the Metropolitan Opera's repertory this season, is being presented by the Brooklyn Opera Society tomorrow night at 8 in the Episcopal Church of St. Ann and the Holy Trinity, Clinton and Montague Streets, in Brooklyn Heights. And also at that time, the Haydn-Mozart Chamber Orchestra will be at St. James Roman Catholic Cathedral, 250 Cathedral Place in Brooklyn.