THIS is the story of how a regular, organized scene on the Cambridge Common has developed on Sundays and how it relates to the growing institutionalization of a hip community in the Boston area.

A year and a half ago Boston didn't have a hip community (defined as a large publicly-recognized group of people identified with no institution--as, for example, universities--other than their common resistance to most of the conventions of the society that was their environment).

As far back as memory goes, it has been recognized that there were living around Boston's bigger universities "colonies of Bohemians." These people were generally considered to speak with "intellectual"-sounding words, wear beards, and, after Harvard professor Timothy Leary's chemical discovery, swallow dangerous drugs.

The dictionary defines "Bohemian" as describing wandering Czech gypsies. The description accurately reflects the extent to which the average man was aware of a different group of people living in his town. That was a year and a half ago.

Last summer 1) widespread media coverage of the use of marijuana by youth in general, 2) the holding of several be-ins in the spring, 3) the emergence of a psychedelic newspaper called Avatar, 4) the appearance of a head shop on Mass. Ave. called "Headquarters East," 5) the creation of a Diggers' free food house on Columbia St. in Cambridge, 6) the opening of a draft resistance headquarters, and 7) the movement of long-haired, funny-dressed people out of such underground (lit.) handouts as the Blue Parrot Cafe into the streets--all these things combined with a lot of magazine ink about the West-Coast gave a name to the now recognized social group. Hippies.

That summer the hip people felt no loyalty to one another, and shared no eagerness in a common interest--the kind of feelings that make a viable community. Most people were sure the head shop would go under and Avatar would fold after the next issue.

THE DIGGERS would up eating most of their food themselves, and never got together again after Mayor Hayes of Cambridge busted them up in his November purge. Headquarters East was a business enterprise that organized no one. And Avatar was published by a tight clique of friends who were interested in reaching the hip people but not in becoming public property. Its editor, Wayne Hanen, was so bombarded with plans to turn his newspaper into a house organ to organize the community that he retreated and let Avatar print the diaries of his neighbors and their children.

After a year of lacking self-confidence and purpose, the hip community is being organized and given a sense of identity. In Boston this work is being done by the City Police. In Cambridge it's being done by a man named Tony Fleming and an idea called the Family Dog.

The Boston City Police did in two weeks what the Avatar couldn't do in a year, but what the New York City Tactical Police Force did in one night at Columbia. With a series of harrassments in which police officers didn't let hippies sit on the Boston Common or stand idle in the streets around Beacon Hill and in which over 200 arrests have been made, the city has given the hip people something to feel together about.

Troy Fleming, however, moved into Cambridge and has been almost entirely responsible for the staging of free rock concerts on the Cambridge Common every rainless Sunday since early in the spring.

Fleming does it to give people, especially hip people, a place to meet and get to know each other. There are a lot of new people moving into Boston, he points out, and the free concerts bring them together so they can do things.

These are old ideas and projects--the philosophy of the Family Dog. The Family Dog was first a rock group, then an organization ("family," Fleming calls it) to give free rock concerts and distribute free food in San Francisco.

The Family Dog first used the Filmore and Avalon auditoriums to put on rock shows. They set up free concerts on the Panhandle, a park near the Golden Gate Bridge. And they ran Monday morning clean-ins in Haight-Ashbury: the city gave them 50 brooms, and they would go down the whole street sweeping.

LAST summer Haight-Ashbury was clogged by traffic jams of tourists ("It took you an hour and a half to drive a couple of blocks," says Fleming.) The clean-ins stopped. And the Family Dog left town.

The group went to Denver and started giving free concerts. At the end of July and in early August, Troy Fleming and a girl named Barbara Taylor split from the rest of the group and came to Boston.