Suppose that you turn on your videotape recorder and make your own copy of a movie being shown on television. Are you violating the present copyright law? That question is now before the Supreme Court and, whichever way the court answers it next spring, the losing side will immediately appeal to Congress to change the law. Next question: should you be required to pay a royalty to the producer of the movie, even if you are recording it in your own home for your own amusement?

Most of the movie producers, not to your astonishment, believe that you should. The recording machines, and specifically the Sony Betamax, raise many fears among the producers. They fear that you might make your own collection of tapes and watch them instead of whatever might be on television tonight. They fear that you will bleep out the commercials. They fear that you will set the machine to record at one time of day so that you can watch at another--a practice that, if it should become widespread, would diminish the commercial value of television's prime time.

The movie producers don't necessarily want the courts to ban the Betamax. But they want to be paid for the right of home recording. Otherwise, two producers told the Supreme Court, the economic base of their whole industry will be eroded, resulting in "cheaper, lower quality television programs and a refusal to license popular, top-quality theatrical motion pictures for television, thereby prejudicing the entire televison viewing public. . . ."

Well, maybe. That argument sounds a bit purple. But let's assume for the moment that it might happen --that the Betamax might make the producers' television rights less valuable. Is there really a federal responsibility to intervene? The movie-makers have proposed a stiff tax to be imposed on Sony, or on the Betamaxes, or perhaps on the tape.

That's like imposing a tax on all Xerox machines on grounds that they might be used to duplicate copyrighted books. Or on all blank paper, since some of it might be used in those machines. To take another example, people in the entertainment and record industries complain bitterly about the common practice of recording music from the radio. But Congress has declined to prohibit home recording, or to tax it.

Copying for resale, or for any commercial purpose, certainly entitles the copyright owner to a royalty. But when radio and television send films and music into your home, the producers have no right to tell you what to do with them there--or to tax you on the suspicion that you might not be watching and listening when, and as, they want. Congress would be grossly wrong to impose what amounts to a private tax, to be paid to the movie-makers, on a whole class of electronic equipment on grounds that some of it might be used to record shows that they have broadcast into people's living rooms.

A generation ago, the television receiver did terrible things to the economics of the movie industry and radio broadcasting--until, after some years, they found a formula for profitable coexistence. Now another electronic device is threatening that formula. It's the job of neither the courts nor Congress to rescue it by extending commercial copyright law into private homes.