NEW YORK (AP) _ The action has been unusually lively of late for the 900,000-plus investors who own shares of General Motors Corp.

In the stock market debacle last fall, GM shares lost some 47 percent of their value, plummeting from a high of 94 to a low of 50. In the few months since then, they have recovered more than half that loss, rallying past 75.

Of course, many stocks have experienced wide swings in the past year. But the behavior of GM has been noteworthy for several reasons.

Given its standing as the nation's second most widely owned stock, outranked only by American Telephone & Telegraph, the ups and downs of GM's price have had a far-reaching impact on the finances and emotions of the investing public.

What's more, GM has long been regarded as a quintessential blue chip, a relatively stable investment supported by a generous dividend yield (6.6 percent as of late last week).

Through the mid-1980s, it lived up to that billing. From early 1983 through early 1987, GM swung back and forth in a range roughly between 60 and 85.

It was only when the long bull market reached its climax last year that the stock jumped to a new high and subsequently toppled to a five-year low.

Certainly, some of that increased volatility can be attributed to the flighty environment for stocks in general. GM holds a prominent place in the market indexes used by professionals in computer-program trading.

But as any casual reader of the business news would readily conclude, there has been more to the story than that.

As a giant enterprise plagued by mounting competition from both foreign automakers and its domestic counterparts, the company has come under increased criticism in recent years about its management decisions and ways of doing business.

The negative reviews perhaps reached a crescendo in mid-February, when Fortune magazine described 1988 as ''the make-or-break year for the world's biggest company'' and carried a cover story in which erstwhile board member Ross Perot described ''How I would turn around GM.''

At the same time, however, many Wall Street analysts who follow the auto industry were taking a different view - that the company was beginning to sort out its problems, cut its costs and improve its earnings prospects.

Chuck Brady, an analyst at the investment firm of Oppenheimer & Co., declares, ''The turnaround at GM continues.

''On the product side, momentum has shifted. GM's products, both cars and trucks, are selling better than last year.

''Internal audits show that quality is up significantly and, by most accounts, style in design is improving too. We continue to believe GM represents an excellent investment opportunity.''

Not all the company's followers on the Street are quite so sanguine. Said Kathleen Heaney of Nikko Securities International in a recent report:

''The major problem, as we see it, is not the company's short-term potential of profitability, but whether GM is capable of building and selling cars that will be competitive with the next generation of Japanese and European vehicles.

''The company is still extremely vulnerable to negative news, and hence our reluctance to jump on the GM bandwagon.''

Wherever it is headed in the future, the recent strength in the price of the stock is heartening to followers of the ''GM bellwether'' as an indicator of the overall market outlook.

Robert Stovall, president of the money-management firm Stovall-Twenty-First Advisers, says this indicator has been bullish since GM shares went four months without matching or going below their Oct. 19 low of 50.

Stovall concedes the patterns in GM's stock chart aren't an infallible guide to the market outlook. The ''bellwether'' got caught in the midst of the flock in the crash last fall.

Nevertheless, he says, ''it is now heralding a summer rally.''