Chances are you’ve heard of Preservation Hall, the legendary New Orleans jazz venue in the French Quarter, home of the Preservation Hall Jazz Band. If you haven’t been there, you might expect it to be a grand and spacious place with many rows of seats, maybe even a balcony or two.

In fact, it’s surprisingly small, with a few humble benches. Built in 1750 as a private residence, it was an art gallery in the early 1960s when Allan and Sandra Jaffe made it a place for traditional New Orleans jazz only: no dancing, no food, no drinks. (Also, no running water, air conditioning, or reservations; if you want to get in, you’ll stand in line.) It has been a sanctuary for the music ever since, except for several months after Hurricane Katrina, when it was forced to close.

Today the Preservation Hall Jazz Band tours the world, spreading the word of New Orleans jazz. This is not the polished, bouncy Dixieland many people associate with the Big Easy. It’s slower, looser and more relaxed, with improvisation at its core.

See and hear the band here (at the Louisiana Music Factory on Decatur) and here (marching through the streets of New Orleans). Then see them live at Orchestra Hall this weekend. They’ve been coming here since 1991. This time, for the first time, they’ll play with the Minnesota Orchestra under the direction of guest conductor Sean O’Loughlin.

Preservation Hall Jazz Band with the Minnesota Orchestra, Saturday, March 20, 8 p.m., Orchestra Hall ($22-$55; $65 VIP). Tickets at 612-371-5656 or online.

What's trad jazz?
What is traditional jazz, and why go to hear it? For answers, I turned to Dick Parker, a former Star Tribune copy editor and assistant news editor who’s also a traditional jazz musician.

Parker plays banjo and guitar with the Mouldy Figs and the Pig’s Eye Jass Band. He has also played with the Bill Evans New Orleans Jazz Band and the Ted Unseth Americana Classic Jazz Orchestra.  He wrote for the Mississippi Rag and currently co-edits Coda for the Twin Cities Jazz Society, of which he has been a member for many years.

So ... what is traditional jazz? “It’s jazz that features group improvisation,” Parker explained. “The instrumentation is generally a cornet or trumpet lead, or a reed instrument, and a trombone, clarinet, piano, and/or banjo, plus bass and drums. It’s not always fast music. It re-creates the sounds of the 1920s and 1930s, before the swing era. It came up out of New Orleans, and to me, it’s like a gumbo of all the cultures there — German marches, spirituals, blues, French quadrilles.”

Why should people today listen to traditional jazz? “Because it’s very entertaining, very engaging. You can’t keep your toes from tapping.”

Would you call it feel-good music? “Not always, but usually. It’s said that if you hear anything with a banjo, you can’t be sad.”

Where to hear it
The Preservation Hall Band is here for one night only. What about the rest of the year? Turns out there’s an active trad-jazz scene in the Twin Cities. Here’s Parker’s list of places to go and bands to see:

Bill Evans New Orleans Jazz Band (descendant of the famed Hall Brothers band). The second and last Tuesdays of each month at Bennett's Chop & Railhouse in St. Paul, 7 to 10 p.m. Reservations recommended. 651-228-1408.

The Mouldy Figs. Every Sunday, alternating between the Mainstreet Bar & Grill in Hopkins, 4 to 7 p.m. (952-938-2400) and Casper & Runyon’s Shamrocks Irish Nook in St. Paul, 5:30 to 8:30 p.m. (651-228-9925). Call for dates.

Sam Fiske. Every Sunday at Merlin’s Rest Pub in Minneapolis, trumpeter Fiske plays two sets of music, one on each side of the Pub Quiz (“Sam’s Sandwich”). The music starts at 7:30 p.m. (612-216-2419).

Pig’s Eye Jass Band. The last Saturday of every month at Eagles Aerie 34 in Minneapolis, 5 to 8 p.m. (612-724-9714). Call to confirm.

The Southside Aces. Jazz jam on the second Sunday of each month at the Nomad in Cedar-Riverside, 5 to 8 p.m. (612-338-6424). Call to confirm.

While the Jack Brass Band doesn’t have a regular gig, and it’s more a hybrid than a trad jazz band, it’s worth seeking out. As luck would have it, the Jack Brass plays this Saturday’s late-night show at the Dakota starting at 11:30 p.m. They’re friends with the Preservation Hall band and a late-night sit-in seems likely.

Pamela Espeland keeps a Twin Cities live jazz calendar, blogs about jazz at Bebopified and tweets about jazz on Twitter.