THE TUNE out of Moscow is changing a bit. In the weeks right after the Polish coup, it was all bluster. Now sweeter sounds can be heard. The premier called for a "constructive dialogue" between his country and the United States the other day, and talked up arms control. The Kremlin is making known its hope that when Secretary of State Alexander Haig and Foreign Minister Andrei Gromyko meet next Tuesday in Geneva, the United States will go along with the long-standing Soviet wish to start START (formerly SALT) talks and to get cracking on a Reagan-Brezhnev summit.

So the tune has changed. The beat, however, goes on. The "beat" is the Kremlin's persistence in regarding Poland as an internal matter in order to fend off Western interest in Poland, on the one hand, and to continue business as usual with the West, including arms control, on the other. Perhaps the Soviets feel that it is time to add evocations of d,etente and better times to their earlier threats of a return to old-style cold war.

Poland cannot be regarded strictly as an internal Polish or Soviet bloc matter. The rights being suppressed there now are rights that the Soviet and/or Polish governments undertook to respect in a series of international agreements dating back to Yalta. The most recent of these was the Helsinki Agreement of 1975. Helsinki, by the way, not only committed the East to observance of certain rights. It is the one formal agreement in which the West has accepted Europe's postwar boundaries. Is Moscow, to shake off its commitment on rights, prepared to release the West from its own boundaries?

We support an eventual start on START and a summit. But why now, before the authorities in Warsaw have agreed to release political prisoners and open talks with the workers and the church? Those are the minimal requirements. Theoretically, it would be better to suspend all diplomatic contacts. Suspending the theater nuclear talks, however, would hand Moscow an enormous propaganda advantage in Western Europe--a chance to recoupwhat it lost when it unleashed the savage Polish repression. Calling off the Haig-Gromyko meeting would deprive the administration of a good forum in which to convey a stiff view of the meaning of that repression to the future of U.S.-Soviet relations. Keeping the engagements already on the calendar, in other words, while making no new engagements now, seems to us a reasonable course.