If you believe that interest rates are coming down because of the recession, you may be thinking of making an investment in a mutual fund that buys bonds.

Open-ended bond funds--usually called "income funds"--are like any other mutual fund. Investors can buy and sell them at any time, for the current net asset value of the bonds in the portfolio.

Bond funds do well in recessions, when long-term interest rates decline. Your interest income may fall a little. But the market value of your shares will rise.

Bond funds do badly, on the other hand, when interest rates rise--usually during periods of economic recovery. You get a rising interest income from the fund. But what you gain in interest, you may lose in market value. If you had to sell your bond-fund shares after interest rates rose, you would take a loss.

Income funds last shone in the recession of the mid-1970s. A-rated corporate bond funds rose an average of 18.8 percent in 1975 and 14.4 percent in 1976, according to Lipper Analytical Services in New York City, which follows the performance of mutual funds.

Speculative bond funds--"junk bonds"--did even better. Lipper's lower-quality corporate bond funds rose an average of 23.8 percent in 1975 and 26.3 percent in 1976. (In all calculations, dividends and interest are reinvested.)

During the recovery years (roughly 1977 to 1980) bond funds did badly. Rising interest rates knocked the stuffing out of them. Corporate bond funds have recovered, but municipal bond funds have been in a disastrous bear market all their own. Tax-exempt interest rates have risen even faster than corporate bond rates--because of the shrinking institutional market for tax-exempts, because of credit worries about certain states and cities, and because personal tax cuts have made municipals less attractive to the individual investor.

If you buy now, interest rates on tax-exempts are high. But if you had owned that fund over the past four years, your loss of capital would have been substantial.

Now, however, the cycle has come round to recession again, which is when bond funds look good. Three observations, before you make an investment decision:

1. Bond funds may be good in a recession, but mutual funds that buy stocks are even better. The Lipper Growth-Stock Funds Index rose 32 percent in 1975 and 16.7 percent in 1976. If you had held on to your growth funds, you would have had a spectacular 1979 (up 27.4 percent) and 1980 (up 37.3 percent)--two years when bond funds were falling on their faces.

Conservative investors like bond funds because of the regular income. But over the last economic cycle, you would have been able to take far more real income out of stock-owning mutual funds than out of bonds. You would merely have taken it in dividends and capital gains, rather than in interest. (Most mutual funds will arrange to send you a monthly or quarterly check.)

2. Another way to invest in bonds is through unit trusts. These are fixed portfolios of bonds, paying a fixed yield, and maturing over a fixed period of time. You can sell before maturity at current market value (which may be more, or less, than you paid). If you hold until maturity, you get your original investment back. "Unit trusts have done about as well as open-ended bond funds," Paul Reed of the United Mutual Fund Selector told my associate, Virginia Wilson.

You buy unit trusts through large brokerage houses, for a sales charge of about 4 percent. Open-ended bond funds can be bought through brokers (at about an 8 percent sales charge) or directly from a no-load fund organization at no charge at all. (For a free list of no-load bond funds, write to the Investment Company Institute, 1775 K St. NW, Washington, D.C. 20006.)

3. Henry Kaufman, of the Wall Street firm Salomon Brothers, forecast last week that interest rates would jump again later this year, in which case bond funds would be losers. On the other hand, if the forces of deflation bring interest rates down over the long term, bond funds are a splendid buy.

Michael Lipper says that in the past, any money in his managed accounts that was not invested in stocks was kept in money-market funds. Now, he says he is putting some of his reserve capital into long-term bond funds, just in case deflation occurs. But, he says, people should be willing to sell their bond funds quickly if Henry Kaufman turns out to be right.