WESTERN EUROPE is now moving sedately toward a political transformation. In June, for the first time, the voters of the European Community's nine countries will directly elect a European parliament. What difference will that make? The answer comes as a duet. The top line is a rather shrill assurance that the new parliament will have -- in the strictly legal sense -- no more authority than the present appointed parliament, and that's not much. But the harmony is a rumble of deeply felt conviction that, in democratic politics, direct election inevitably confers power of the most substantial kind. Nobody in Europe really doubts that, with the June elections, the national governments will shift the balance fundamentally toward the larger confederation that they have been creating over the past three decades.

The other thread of the European movement, the common currency, leads in the same direction. The European Currency Unit -- the ECU -- was supposed to have gone into effect at the beginning of the year. It was postponed at the last moment; the official reason was the endless quarrel over agricultural subsidies. The real reason appears to be that France's President Valery Giscard d'Estaing wants a little more time to deal with the Gaullists. As always, they are adamant about any sharing of sovereignty. But President Giscard appears to be winning that argument, and the delay is probably no more than temporary.

The European movement has unexpectedly picked up new strength in the past couple of years. At the beginning of this decade, the Common Market was talking about a monetary union by 1980. Then came the oil crisis, knocking all the countries in different directions. In the confusion, the currency idea seemed lost. Casting about for an alternative way to strengthen the European principle, the governments agreed on a directly elected parliament -- a remarkably daring venture in a time of great uncertainty and dissension. Then, within the past year, in response to the fall of the American dollar, Mr. Giscard d'Estaing and Germany's Chancellor Helmut Schmidt suddenly revived the common currency. They wanted urgently to protect Europe's internal trade -- and the jobs depending on it -- from the chaos in the exchange rates. Now, once again, things are moving rapidly toward closer confederation.

It is France, essentially, that sets the pace. The Gaullist position has always been a vehement defense of national sovereignty. But the present government is inclined to think that absolute sovereignty is an illusion for a middle-sized country with the Americans on one side and the Russians on the other. In a speech a couple of months ago, Premier Raymond Barre said, "We want a Europe that is in control of its future.... We see Europe not as a pawn but rather a link between East and West...."

The German interest is a bit different. Over the past several years, Germans have been desperately uneasy about the prospect of isolation between the Soviet bloc and, to the west, countries eroded by wildfire inflation, social instability and a drift toward Eurocommunism. The Germans have consistently supported a stronger and more tightly bound community, even if it means -- as it surely does -- that they will have to pay a lot of the bills. As for the other seven -- Britain, Italy, the Netherlands, Belgium, Denmark, Ireland, Luxembourg -- they are coming in because, in varying degrees, they believe in the European principle and, as a practical matter, they don't want to be left out.

The approach of the June elections is already beginning to have interesting effects on politics in the nine countries, as candidates begin to maneuver toward new alliances across national boundaries. The currency plan is important but, as experience suggests, it may well come apart under pressure. A parliament will not have so immediate an effect on the daily affairs of the community. But it seems very likely that the habit of direct elections will prove irreversible.