It begins, inevitably, to the strains of the "Song of the Volga Boatman," for which each of us can supply his own words from youthful parodies.

But the National Geographic's hour-long special on the mother river of Russia is more than your standard travelogue tonight on public television (Channels 22, 26, 8 o'clock). Its special interest is what film - taken with rare permission from the Soviet government - was allowed that what the American narrator has to say in commentary.

The visuals are spectacular at times as we see the gold onion-domed towers of the Great Catherine Palace, a dancing troupe whirling in the fields for rural villagers, the black pearsl of caviar being harvested from sturgeon bellies and strong, stoldi peasant faces.

American film producer Irwin Rosten, who wrote and directed "The Volga," and his camera crew spent 4 1/2 months in Russia for the filming. They were accompanied everywhere by television officials from Novosti, the Soviet News Agency. But no film was censored, and it all left the Soviet Union in sealed cans to be developed in the United States.

Without the understated commentary, you might be seeing scenes from a Soviet propaganda film with modern factories, patriotic ceremonies, happy people at work and play.

There are the state-run nurseries for young children, as winning as only happy young children can be. Then narrator Jack Palace points out that almost from their first steps, children learn to live in groups and, as a Soviet teaching manual explains, the objective of education is to form a collectivist, a person who does not think of himself outside society.

The cult of Lenin is felt throughout much of the film with omnipresent status and pictures, and the irony is not missed that his widow once pleaded: "Build no memorials to him . . . he placed no store in such things."

And then there is the intense patriotism of the Russians - seen in their faces beyond the show of government sponsored ceremonies. On Victory Day (May 9), there is an incredible outpouring of people and emotion in the tremendous Hall of Military Glory in Volgograd, the renamed city of Stalingrad. It is strangely moving even viewed through American skepticism of patriotic display.

"The Russians never call it World War II. It is for them the Great Patriotic War," producer Rosten, here for a preview, explained last week.

But then, as the narrator reminds us, Russia lost 20 million people, almost 12 per cent of its population, in that war.

The camera crew spent about three days on the flagship of the Soviet cruise fleet on the Volga, the Lenin. It was a rare occasion because the Lenin takes only Soviet workers on vacation cruises. What was reassuring was to see only a few did get up for early-morning exercises and they share the same bulge problems with many Americans.