The music between its three stages ran nonstop for nine straight hours, but the vibe was as laid-back and unfussy as ever. The lineup was loaded with niche acts who often aren’t easily categorized. The organizers, sponsors and concessionaires were almost all local and independent. And the cost for a ticket was on par with a parking fee at other big summer concerts.

But don’t just take this reviewer’s word for it that the Roots, Rock & Deep Blues Festival is consistently the coolest and most enjoyable music-led block party in Minneapolis.

“This festival is just a really well-oiled machine,” veteran Iowa picker William Elliott Whitmore raved Saturday afternoon to the RRDB fans dancing to his Southern rocky band Middle Western outside the Hook & Ladder Theatre.

“In my opinion, this is the best festival put on in the cities,” Colin Campbell of the Shackletons added an hour later to a crowd that bulged out the open garage doors of the Mission Room, a new, smaller sister space to the nonprofit venue.

Housed near the corner of E. Lake Street and Minnehaha Avenue in south Minneapolis, the Hook & Ladder took over the ninth annual Roots, Rock & Deep Blues marathon two years ago after the event went through several transformations. It originated simply as the Deep Blues Festival, then evolved into the block-party format helmed by the sorely missed Harriet Brewing.

While the H&L team has stayed true to the fest’s bluesy roots — Muddy Waters, Howlin’ Wolf and Buddy Guy songs were all still covered Saturday — it has expanded the lineup to also include a vague but somehow sensible mix of Americana, country and rootsy punk performers.

In fact, the last act to perform at this year’s festival was the indie-rock power trio Gully Boys, a band of hard-cranking young women who probably would’ve been a better fit at last month’s Rock the Garden music fest. Here, though, they helped draw a fresh crowd to see RRDB regular Erik Koskinen on the next stage over, just as fans of the twangy guitar and songwriting maestro took a gander at the Gully Boys.

A sign of its more varied but viable approach, Saturday’s RRDB opened with sets by 92-year-old jazz and blues piano plunker Cornbread Harris and twentysomething folk-rock strummer Siri Undlin, aka Humbird. Each were among the day’s highlights, too.

Undlin’s acoustic set showed off the Laura Marling-like blend of barbed but beautiful, Irish folk-tinged melodies in a rawer form than the atmospheric power of the full Humbird lineup (an electric trio hosting an album release party Sept. 7 at the Parkway Theater). Harris, meanwhile, showed that his groove-generating skills on the ivories are still as sharp as his wit.

Introducing one of his many Count Basie interpretations, the ’50s-era supper club vet boasted, “There are many other arrangements of this one, but only a couple are as good as mine.”

Koskinen drove two hours from an outstate gig to make his RRDB set in the main Hook & Ladder indoor space with minutes to spare, and he still sounded rock-steady.

The Upper Peninsula native stresses his character-driven Americana songwriting skills on his two-month-old record, “Burning the Deal,” but with fellow ace Paul Bergen he showed off why he’s also considered one of the Twin Cities’ best guitar players. Their gritty country-rock dust-ups weren’t the kind of guitar jamming typically heard at a blues fest, but that didn’t matter.

Before the Koskinen set, Bergen also backed Becky Kapell through torchy versions of her wry but romantic country tunes (sample lyric: “I kissed you, and it burned”).

Several other types of jamming went down in the parking lot outside the H&L, where Mae Simpson, Kind Country and Middle Western all heated up the hot day. The latter group — made up of members from around Iowa and Illinois — laid down a blend of lap-steel-laced stoner-rock and Leon Russell-like piano boogie, while the Minneapolis-based Simpson sounded like Melissa Etheridge fronting a horn-addled funk and soul unit.

As for burgeoning Twin Cities sextet Kind Country, the acoustic string band played an over-trampled brand of fast-picking alt-bluegrass that sounded too muddled and busybody when both pedal-steel and harmonica were also thrown into the mix.

Pedal-steel was a big factor in making Eleganza! one of the day’s most electrifying standouts, literally and figuratively. Former Chooglin’ frontman Brian Vanderwerf and his Stones-y twang-rock quintet steamrollered through songs from their richly rowdy new album “Full Length.” The winter-hating “Alabama Bound” especially sweltered in the late-afternoon heat.

Following Eleganza! in the comfortably open-air Mission Room, Stillwater-reared sibling rock trio the Shackletons unexpectedly but convincingly turned in a couple of blues tunes, including Howlin’ Wolf’s “Killing Floor.” Afterward, frontman Campbell joked, “Since we played a blues song at a blues festival, the rules are we get to play a new song.”

Those walloping but hook-filled new tunes played by Campbell and his two brothers/bandmates only added to the buzz around the wild-eyed trio, who also turned in a version of Camper Van Beethoven’s “Take the Skinheads Bowling” to underline their fun-loving, punky side.

While a wide array of styles were heard throughout the day, St. Paul-based singer/songwriter and guitar slinger Mary Cutrufello effortlessly connected many musical dots just in her one fiery set, from the Springsteen-esque anthemic rock of “Worthy Girl” to the alt-twang of “Panhandle Wind” to the bluesy groover “Honey Chile,” which she herself aptly described as “Al Green meets ZZ Top.”

Coincidentally, Cutrufello came up through the same Austin, Texas, music scene as the band that will probably earn the biggest local buzz off the 2019 RRDB fest, the Peterson Brothers.

College-age siblings Glenn and Alex Peterson played their set like a NASCAR race, strategically speeding their way through a twisty-turny play­list of old R&B, funk and blues tunes. Each version had their own unique spin, like the crescendoing jam through the Dramatics’ “What You See Is What You Get” or the version of Green’s “Take Me to the River” that sounded like it originated on Stevie Wonder’s “Innervisions” — all with Glenn soloing on guitar with the same flashy but fulfilling approach as their recent tourmate Gary Clark Jr.

Don’t be surprised if the Petersons wind up at the Bayfront Blues Festival or headlining First Ave or the Dakota in the coming years. If they know a good thing when it hits them, though — and where they were an unequivocal hit — the brothers will make it back to the RRDB fest sometime soon, too.