On Massachusetts Street, the bustling patchwork of life and culture that defines downtown Lawrence, few things can be guaranteed or predicted. The cultural tectonics shift daily. But for decades, street musicians — their names and faces always changing — have been one of the most familiar and reliable aspects of the landscape.

Known traditionally as buskers, street musicians have historical roots stretching as far back as the 12th- and 13th- century French troubadours and trouveres, the traveling poet-musicians of the day, says Doug Harvey, a performing musician and adjunct professor of history at Johnson County Community College. Today’s street musicians are generally found in college towns like Lawrence and large cities across the country.

Musical street performance, or busking, has traditionally been seen as a moneymaking enterprise, but the intentions of Lawrence street musicians are as varied as their instruments and style.

“Some folks are playing to get spare change, other people play because they like to play,” says Brad Butler, a slight, dread-locked man noodling on a classical guitar during an unseasonably cool Sunday afternoon in a cozy alcove next to the Antique Mall, 830 Mass. St.

But because some street musicians here accept tips, their playing is sometimes perceived as invasive entertainment, if not outright begging. For most street musicians, however, the music is more meaningful than mendicant.

“I’m not trying to scrounge a dollar,” says Chad Smith, strumming pop chords in the same alley a day later. “If you want to throw a dollar, that’s great. I’m here to express myself.”

That current of self-expression runs parallel to a sense of creative and physical freedom many of these musicians share. Butler, a recent Lawrence transplant from Colorado Springs, Colo., says he can play “under a tree, under a rock, anywhere I want — grab a coffee, pick a spot and sit for a bit.”

Though the possibility of playing under a tree or rock exists in theory, most street musicians in Lawrence prefer the four-block stretch of Mass. Street pavement between 7th and 10th Streets. Three of the most popular places to play are in the alley next to the Antique Mall; the wide expanse in front of U.S. Bank, 900 Mass. St.; and on the corner of 7th Street. These venues receive heavy pedestrian traffic and have moderately comfortable seating (insofar as concrete can be deemed comfortable).

Ignored or avoided by some when playing these ad hoc venues, street musicians exist as a living soundtrack in the lives of others.

“It’s for people who can’t afford to go to the bar and buy the beer,” says Tara O’Brien, JCCC sophomore, stopping and listening to Butler play. “It shows how much music is in this town and how much people love it.”

Because street musicians have played on Mass. Street for so long, by default, they have helped shape the character of downtown Lawrence and distinguished it from the rest of the city. Larry Billings, owner of the Antique Mall, says that when street musicians play, they give downtown “a different kind of atmosphere — a carnival atmosphere.”

But this is far from the Golden Age of street musicians in Lawrence. Billings, who has owned the Antique Mall for 14 years, says street musicians don’t appear outside his storefront as often as they once did. Musicians used to show up as many as three times a week. Now only one a week stops to play, generally on the weekend.

Harvey says the nature of street musicians in America is cyclical, an ebb and flow of performers dictated by the social climate. And, Harvey adds, street musicians in Europe are more prevalent because Europeans are more accepting and appreciative of the performers and the lifestyle.

But as long as one musician picks up a guitar and perches somewhere on Mass. Street, the tradition here will continue.

“It’s something people have always done,” says Smith. “Someone will always be playing downtown.”