WHEN HARVARD SQUARE was looted and rioted at the turn of the last decade, the first buildings to go were the boutiques and the banks. They smashed out all the plate glass windows, threw Molotov cocktails, and took particular relish in destroying those fashionable, hip boutiques.

These were stores which sold things like love beads and candles and dayglo posters, and of them all, only The Truc stands erect. Legend and lore tells us these small businesses were merchandisers of "the movement," run by classy entrepeneurs who saw a gold mine in the nation's dissident youth.

"I'm not sure what music is today," Eric von Schmidt says. "The word is applied to punk rockers and discos and everything down to bubble gum... I wonder when they're going to get to the pablum audience."

Popular music today is a serious business--with contracts, promoting and merchandising, and it all comes out looking like so many cans on a super-market shelf. Nevertheless, America's last three decades have fostered small but musicall potent "scenes." Eric von Schmidt is a lover of Cmabridge's own folk scene, and his 309-page book, Baby Let Me Follow You Down documents it all in words and photographs. Most would say this scene went out of existence with the last Molotov cocktail that flew through the window of the Charlesbank Trust Co. But to von Schmidt, the Cambridge folk scene survived the flames and cultural demolition which devoured "the moment" at the end of the '60s. The Cambridge folk scene, he asserts, is a part of American musical history--not as a fad, but as a unique, valid and genuine musical "scene."

Von Schmidt examines the roots and characters of the Cambridge folk scene from its inception in the late '50s, entering old coffee houses like Tulla's--once near Cahaly's--that first heard the voices of young folk singers like Joan Baez. This was in 1957-58.

ALL THE NAMES. Joan Baez, Mimi Farina, Richard Farina, Dave Van Ronk, Bob Dylan, Leonard Cohen, Tom Rush, Pete Seeger, Taj Mahal, Geoff Muldaur, Bonnie Raitt, John Sebastian, all spanning a decade. Von Schmidt sees an enduring musical "scene," based on the fact that people wanted to hear this music. Today that scene doesn't exist, and while von Schmidt wants badly to believe that the listeners are out there, he acknowledges popular decline of the folk movement, and the powerful appeal of electronic music.

"Electricity changed it all. It brought an overwhelming feeling to popular music. It shows the power of sound, and it has a lot of appeal. Folk music is less self-indulgent, it is more conversational.

"This book is an attempt to recount that era," von Schmidt adds, "to show that this existed, and that it may happen again." The author balks at considering folk alongside other American "scenes," such as any rock and roll scene, including today's burgeoning punk/new wave scene.

"Punk seems very self-indulgent to me, at least in this country. I think it draws a lot of upper-middle class audience....Folk music is musically valid because it relates the reality of experience as opposed to analytical considerations; it encompasses humanity in a way tht no popular music does."

Von Schmidt's bias gives his book its power. His knowledge and understanding--both of the folkies and their detractors--lends credibility and a certain ghostliness to his recall. Baby Let Me Follow You Down succeeds where many "rockumentary" efforts fail--these are not idle memories scribbled down for pleasant reading; they are real experiences.

"We were so innocent," many of the book's characters say. They came to Cambridge for nothing more than a college education. "Education," von Schmidt points out, "is the key to the American dream." Then a job. Then a home. And a family. And then Woody Guthrie's refrain: "Then they all live in boxes, little boxes, all the same."

Von Schmidt's innocent characters all came for the university. Baby tells us, indirectly, what they learned:

So,where no scene had existed before, one came into being. What had been smouldering before burst into flames. Joan Baez was the most prominent member of a group whose numbers were growing daily, as were their abilities as musicians and performers. More important still was the fact that there was an audience for this music. People wanted to hear it. It filled some need that we all shared in common before we ever knew what it was. Whatever plans we might have had before were to be totally changed.

THEIR INNOCENCE was hardly contrived. They knew nothing about folk music, about coffeehouses, about the honest blues. But like all musical scenes, the folk scene had a magnetism, (emanating) perhaps from the "flat pink and charcoal stretch known as the Eisenhower years."

Many of the younger performers coming up came out of what we called "The Silent Generation" and were apolitical. But they had something else going for them which related. They were a post Kerouac group who were somewhat Bohemian in outlook and lifestyle. I looked at the broader picture, and they were part of a scene that was very important to me. I didn't know how that scene was going to develop. But whatever was happening, I wanted to find out.

Von Schmidt looks back on the Cambridge folk scene and its voyagers as tellers of need. They are the real breed of folk tradition, musicians who formed direct experience into art.

"I hear kids today listen to music and get lost in it," von Schmidt complains, 'and escape into it." They'll say that folk's boring or its too soft or too slow, and I'll say, 'Well don't you think it's more sensitive?' But when people need to figure out what's going on in the world and who they are, when the energy crisis comes on so bad that middle class people are out in the backyard chopping up wood, I think you may see a resurgence in this type of music. It's sensitive, it's based on direct experience, and it's conversational--it tells a story, it tries to relate. It doesn't just scream."

THERE IS SOMETHING ETERNAL about folk music--especially the blues-- which makes you believe everything von Schmidt says. Musicians like Muddy Waters and Mississippi John Hurt--and even Pete Seeger--have been playing their music to adoring ears for generations. The best folk becomes so personal and compassionate that in a world of strangers, it's better than a friend.