THE RECORDING begins as happy as an Easter morning, with a solo piano marching through the theme, a simple tune like sunrise itself.

The song is entitled "God's Love (Made Visible)." The first time I heard it, I thought of Handel. It sounded like one of those triumphant Presbyterian processionals when the choir comes streaming down the center aisle and the whole church is on its feet singing.

But, on the second chorus, the sound changes, as seamlessly as life itself. This swinging piano is joined by an electric bass and the smart kick of a drummer. And playing off the piano line is the circus sound of an electric keyboard. Then the piano takes off merrily in Spanish improvisations. Suddenly, this traditional Christian anthem sounds modern and joyous and international, like the best brightest moments of rock'n roll.

This record is Dave Brubeck, jazz pianist and composer, playing with his three sons, Dan on percussion, Darius on keyboard and synthesizer, Chris on bass. If one needs insipiration on an Easter morining, listen to this record ("The New Brubeck Quartet Live at Montreux") and ask yourself how pleasing it must be for a great name like Brubeck to reach the day when he is playing with his own sons, who are grown and accomplished, in their own right, different from him yet also in accord.

"We love to play that tune," Brubeck said. "It's really a joyful piece."

As he tells it, the song was composed in the back of his VW bus, driving to Vermont. Brubeck had finished, he thought, a new Mexican cantata for Christmas.His wife, Iola, who was driving, said the cantata wasn't finished. She said that he had left out the most important theme.

What's that?

"God's love made visible."

Brubeck wondered how that would fit a Mexican rhythm. "Say that again. Just keep saying it."

God's love made visible.

He is invicible.

"You know, Brubeck said, "that's perfect for 5/4."

So Brubeck wrote this wonderful song in a Vermont cabin in August and it is now the concluding theme of his cantata, "La Fiesta de la Posada." He and his sons recorded it at the Montreux jazz festival in Switzerland when they were touring together in the summer of 1977.

My son gave me this record last year, a sentimental gesture because he knows I grew up on Brubeck, a birthday gift which also opened my mind to what has been happening in American for some years.The word that some music critic or record company dreamed up is "fusion." They write about "rock-jazz fusion" and list a growing number of musicians who genuinely bridge between the two, not simply in electronic instrumentation but in style and rhythms.

I like the word-fusion-because I think it describes a social reality larger than music, a process of education that is underway in America, mostly ignored by social critics. I saw it develop in my son's musical taste. And my own, for that matter. He started with the conventional list of rock stars and, as he became a serious musician himself, his interest and appreciation took on an extraordinary range, from Frank Zappa to jazz and classical. Brubeck is not his favorite, by any means, but he listens with respect. He understands subtleties that are way beyond me.

Brubeck is Brubeck, his own singular traditional and actually not anywhere near the center of the movement called "fusion." But he understands what is happening, from his own sons, from their music, and what he sees is a cause for celebration.

Back in the Fifties, Brubeck's music sounded cool and cerebral, swinging but also aloof, with the subtle lyricism of Paul Desmond's alto sax and Brubeck's own complex melange of classical and jazz lines. This was music for your serious, alienated white kids who wanted to rise above the general trash of their native civilization.

The Sixties blew away that music, in a sense. Rock'n roll stomped all over subtlety. It kicked down the studio door and ran jazz musicians off the stage. The times required a new outlaw music, an angry romantic message more funky than jazz itself, a loud audacity that divided generatons, including Brubeck's.

His sons were already playing, forming rock groups, recording and touring. Brubeck did not think much of the new sounds or the new young musicians he found sleeping on his living room floor.

"At first, I was completely turned off by the long hair and the way they dressed, but when I got to know them, I realized they were just fantastic guys, people who could play anything-rock, blues, jazz, classical-fantastic musicians.

"when you see the caliber of these young people, you've got to be very narrow not to see that there is something valuable in rock, if these guys like it."

Brubeck, like a lot of parents who grew up on earlier sounds, was forced by his children to reexamine rock and understand its message, to appreciate its authenticity. Rock is, after all, only a different derivation from the same source that feeds Brubeck's music-the jazz feeling created by American black people.

"A different thing happens in art," Brubeck explained, "when the country goes wrong. The kids protested and they started playing a music that was separating them from institutions and from their parents. They became alienated and removed because they didn't have a reason to respect the institutions and the government at that time.

"To me, they went too far. Having five sons and a daughter, the discussions at our house were really wild. But who can say they overreacted? That war almost destroyed this country. They were right to protest."

What Brubeck is suggesting reminds me of Kurt Vonnegut's wonderful line about how artists-musicians and painter and writers-serve the society like canary keels over, you know the country is in deep trouble. In a way, that's what happened in the Sixties, not merely in music. Desperate messages from the young required new sounds, desperately stated, demanding that the rest of us listen.

That era did not end; its sound continues in many ways today. But I think it is more accurate to say that American society is now in an era of "fusion," like jazz and rock, borrowing from each other, showing a little more respect for differences. Like Dave Brubeck and me, learning from our children.

Any serious examination of how American has changed in the maligned decade of the Seventies must acknowledge that the barbarous message of the Sixties got through-that in trivial and profound ways older people did listen to the rock culture and absorb much of it as their own.

Brubeck today is abundantly optimistic, envisioning "a mosaic of world music" which will emerge and include everyone, every culture. "I really think it's the most exciting time of all to work as an artist," he said. Why is that? "Because the audience is ready for anything."

Most social critics still address the war between the generations as a raging conflict. Meanwhile, a lot of the foot soldiers from both sides are down at the spring, filling their canteens and exchanging addresses. Brubeck runs into a young people all the time who tell him how much their music is influenced by his. He has to listen hard sometimes to believe it. But he is listening.

Only the narrowest minds, young and old, will not see the celebration of "fusion." As Brubeck says, "fusion" is what has always gone on in music, from Beethoven to Brubeck to Zappa and Miles Davis. Social change in America follows the same beat.