AREFLECTION on Bob Dylan's return to Boston must account for one fact--his near-Messianic hold on the 31,000 people who made it to either of his two concerts last Monday. His music can be judged. His words will be analyzed. But that analysis should add up to an explanation of the central phenomenon: After nine years away from Boston and roughly three years since his last album of original songs (not counting the soundtrack to Pat Garrett and Billy the Kid or Columbia's recent collection of rejected tapes from Dylan's Self-Portrait sessions), Dylan scored a triumph. Two packed houses rose to sing "Like a Rolling Stone"--nine years after Dylan inaugurated folk-rock by playing that same song at the Newport Folk Festival, nine years since people first cried that he had sold out.

That the audience loved his music is easy to explain. The Band, probably the most talented American rock group, again proved its discipline, energy, and versatility. The group's lead and bass guitar playing, the keyboard work, and particularly the singing of Levon Helm were outstanding. In the evening concert, Dylan fit in easily with the group, coordinating his rhythm guitar with the Band better as the performance progressed. During their two solo sets, The Band played mostly old songs. "I Shall Be Released," which Dylan wrote, and Robbie Robertson's "The Weight" and "The Night They Drove Ol' Dixie Down" were outstanding.

Dylan's skill and judgment were spectacular. His set on acoustic guitar was disappointingly short, but he paced the concert perfectly. In a fairly smoothed-out version of his old-style folk-blues voice, Dylan sang forcefully, sometimes threateningly. He must have spent some of his time in Wood stock practicing harmonica, because his accompaniment to "Don't Think Twice, It's All Right" showed more skill on the mouth harp than anything he has ever recorded. Even Dylan's single piano solo was dramatic: "Ballad of a Thin Man" was one of the evening's most striking per formances.

But it was not music alone which won the audience. Dylan earned his first standing ovation before he played a note. Ten years ago, Dylan stood for a potent strain in the American mood, a libertarian current last exemplified in folk music as forcefully by Woody Guthrie. Today, Dylan stands for essentially the same thing; it is only that the times have changed so that people appreciate him more.

BECAUSE DYLAN emerged during the peak of the civil rights movement and began to hit his stride at the time of such breakthroughs as the Berkeley Free Speech Movement, his pacifism and libertarianism were automatically identified with the left. Those were friendly days when whites still worked with SNCC and the distinction between political and cultural radicalism was hazy. Singing songs then seemed a political act --if enough people sang, blacks would withdraw have social equality, U.S. soldiers would withdraw from Vietnam. Smoke-ins looked like acts of political defiance and demonstrations liberated the spirit as much as they dramatized demands.

But Dylan's songs were never expressly political. His evocation of the image of Guthrie, whose leftism was also more a matter of moral common sense than of specific tactics, was embodied chiefly in an imagery of highways and railroads. Dylan had to construct his own hard times to live through:

I was making my own depression

I rode freight trains for kicks

An' got beat up for laughs

Cut grass for quarters

An' sang for dimes

The oppressiveness he sang about was not the misery of poverty but the stifling complacency of middle class comfort:

'Cause you can't find (hope) on a dollar bill

And it ain't on Macy's window sill

And it ain't on no rich kid's road map