"Thus we took leave of the Friendly Islands and their inhabitants after a stay of between two and three months, during which we lived together in the most cordial friendship."

From the Journal of Captain Cook, July 1977.

TONGA, BEFORE it is anything else, is a song. Whether it's schoolchildren sitting under a banyan tree singing traditional Tongan melodies, or the Wesleyans and the Catholics trying to out-hymn each other on a Sunday morning, it's a rare breeze that doesn't bring a song and a rare evening choir competition that doesn't easily outdraw the Kung Fu movies.

Tongan songs have charmed more than one illustrious visitor over the years. Dutch navigators arrived in 1616, and the islands subsequently hosted Tasman, Wallis and Captains Cook and Bligh. Tupou the First established a monarchy in 1845, introduced parliamentary government and gave his people a constition. His line still rules Tonga today, but the "Friendly Isles" (as Captain Cook called them) are now part of the British Commonwealth.

What, exactly, do King Taufa'ahau Tupou the IV's 92,000 subjects have to sing about? Certainly not their lot. They live on 36 of the Kingdom's 169 islands spread out over 140,000 square miles of the South Pacific, 1,100 miles northeast of New Zealand, and fish and farm to keep food - mainly root crops - on the table. On the other hand, there are a lot of fish and root crops, so who's a Westerner to complain?

Some Tongans, however - 33 to be exact - have more to sing about than others. These are the hereditary nobles who own much of the land and make most of the money. Time was when every Tongan boy, upon reaching puberty, got 8 1/4 acres of land to do with what he would, but land is running out and sexual awakening - aside from its intrinsic value - is no longer the boon it used to be.

Technically, Tonga is still the constitutional monarchy Tupou the First invented, with a legislative assembly composed of "seven people representatives," as one brochure puts it, and seven nobles representing the 33. Not exactly one man, one vote, and not exactly popular for that reason. Atop this pyramid sits his majesty Taufa'ahau Tupou IV, who traces his ancestry back thousands of years into the mark where history and legend bed down together. He used to weigh upwards of 400 pounds, but dieted a hundred off recently and looks and sounds much better. His majesty lives in a palace on the waterfront in Nukualofa and is reputedly a friend to man. This trait, friendliness, is rarely attributed to kings, but Tupou IV has apparently earned the encomium. Some stories make the rounds.

For example, custom dictates that in the royal presence one does not drink before the king has partaken. At an audience granted to some American officials, one untutored Yank raised his glass and was just seconds short of an international incident when the alert monarch dashed his own glass to his lips and saved the day. But some say this story's epilogue bests its begetter.

The incident, it seems, was made part of the briefing for all palace-bound visitors. A group of Peace Corps officials was served a light beverage at a later audience and looked knowingly at each other, waiting patiently for his highness to drink. At length he did and they all followed suit, setting their glasses (from Sears mail-order house, the story has it) back on the table. Then a look of horror came over their faces: Does the same protocol govern the second and all subsequent sips as well? They decided it did and there-after drank as a team.

When you go to Tonga there are two things you should do; go to church on Sunday and visit an outer island. The first you do to understand the place, the second to enjoy it.

On Sunday morning the bells ring out over Nukualofa like it's the Second coming and the Messiah is kicking things off right here in Tonga. Dressed in their best, the faithful - everybody - gather to worship the God the missionaries brought for them. Their "best" incidentally, includes a wide woven sash worn at the waist, the older and more tattered the better, representing the ragged sails of their ancient boats at the end of an arduous passage. The sashes symbolize respect and humility for the gods that got them through and are worn, accordingly, over their Sunday finery.

The inside of the church is bedecked with elaborate banners honoring the recent dead. The minister makes his way slowly up the steps to the lectern. He is wearing sunglasses.

Suddenly the congregation is on its feet belting out hymn 651. And they don't fool around. Not for them, the cacophony of an unassimilated rabble, but the harmony of a trained choir - women leading off in certain parts to be joined later by men, other parts beginning softly and building to power; the whole done as if rehearsed late into many a Tongan evening. Then they sit down and the real choir takes over. And if you thought the congregation could sing.

Then it's time for the children's sermon. It's about the bat, the eagle, and the dove and how they were told by their parents to stay home. But they disobeyed, gussied themselves up for a night on the town and were eaten each and every one by the fox. Enough said. All the while a man with a long rod sneaks about and whacks the pisty back into miscreants.

Another hymn and then it's time for the main event, the sermon by the man behind the dark glasses. I don't understand a word of it, so I concentrate on his style - and it's very good. he starts out low key, like he'd just run into you on the street. But there's a rhythm. Then he gets a little more agitated, starts carving the air with his hands. Before long, he's mad, pulling out all the stops - shouting, pounding on the railing - and damn if the wind doesn't come up, setting the banners rocking, as if the dead themselves have come back. And then, after reaching his peak, he brings it down so low people are leaning forward and straining to hear. And then he turns it all off and ends up matter of fact, as if for a moment he'd been possessed but he's back to his old self now. Later, I learn he is blind and has talked about his cross and how happily he bears it.

The Methodists, Wesleyans, Cahtolics, et al, have done their work well, all in all; but they wouldn't have been too smug if they had attended this same church's fund raiser held the night before to help out the shcool, which had been partially destroyed in a recent earthwquake. Tongan dancing was the lure. Young girls, their skin glistening with coconut oil, swayed to the decidely secular music while the generous came forward and pasted their contributions onto these dancing daughters. When there was no more skin to cover, the donations were peeled from the human treasuries and the process begun anew.

Property chastened, you're ready (on Monday that is, since the Sabbath is strictly honored in Tonga) to go out and encounter the Tonga that Captains Cook and Bligh called at. Don't look for it in the capital. Head instead for the islands north of Tongatapu, the main island. Take Vava'u, for example. It's 170 miles to the north, accessible by air or sea - a beautiful high island with a great natural harbor, reached through a majestic fiord-like approach. Here on Vava'u you begin to understand why the official Tonga visitors brochure bears this boast on its title page: "April 1977-Valid Indefinitely."

This is the Tonga of breadfruit trees, of banana, mango, pandanus, fern and bamboo trees, of night-blooming jasmine, of breezes bearing the essence of frangipani (a scent so rich and heavy it stops you in your tracks), of young men with hibiscus tucked behind their ears.

As the book says, nothing much changes here, and it's a good feeling. Not that there isn't a lot to do; great snorkeling in coral straight out of National Geographic, fish beautiful enough to take your breath away, spearfishing (if you can kill color like that), swimming, shelling, boating to nearby uninhabited islands. At night you can go to the Vava'u Club, catch a not-too-recent, not-too-good movie or go to a choir competition and listen to the battle of the sects.

But you can do something even better on Vava'u, almost have to, in fact: You can lay back. Something happens out there, something to do with the smells, the breeze, the singing, the smiles - a kind of heaviness descends on you and takes the sweep out of your step, the sting out of the need of the moment - like if you can imagine time a little tipsy. Finally, it's visceral, a feeling in the muscles, in the bones - a soothing sensation that words such as calm and peace try to describe. You can, if you'll let yourself, sink out of yourself for a time and just be.

And when it's over, take a deep breath, get on the little SPIA plane at Lupepau Airport (two chairs, a table for immigration and another for health and custom), and fly to Pago Pago in American Samoa to pick up your Pan Am flight. And, if I were you, I'd steer clear of the "native dancers," who are right there at your gate (as 1 a.m. no less) singing and shaking for the groggy tourists who are stumbling onto the Australia-San Francisco-bound 747.

You know it's not like that. You've been where people dance because they feel like it. And sing because they like the sound of their voices. Where people are in bed at one o'clock in the morning.