Here’s an idea: What if they put together a music festival for people who… like music? That’s crazy talk, right? But not necessarily to the organizers of the inaugural Arroyo Seco Weekend, held in Pasadena June 24 and 25, which had the radical idea that you could put some venerable jazz and soul greats on the same bill (if not in the same prime time slots) as some indie and mainstream rock marquee acts without sending anyone into paroxysms of demographic confusion.

You could look at it as Goldenvoice cleverly looking to fill the vast gulf between the twentysomething-targeted Coachella and sixty-something-oriented Desert Trip with an easy-to-access venue (a golf course) just outside Los Angeles. Or, you could view it as lifestyle marketing aimed at the kind of people who consider themselves immune to lifestyle marketing. Or, you could see Tom Petty, Weezer, the Shins, and the Preservation Hall Jazz Band on the same lineup and not look a gift horse in the mouth.

If there’s one word that might describe the vibe organizers were hoping to achieve, it would be: chill. Mission mostly accomplished, on that score… except for the literal part, as traditional June-gloom weather patterns in Pasadena gave way to triple-digit temps on day 2. “Guys, you are my champions today — you’re cookin’ it, but you don’t give a f—!” exclaimed Fitz and the Tantrums singer Michael Fitzgerald, during a mid-afternoon set on the festival’s main stage. A little later, he was forced to concede that giving a f— was maybe a good idea after sighting someone in the packed crowd who seemed in distress: “Let’s all stay hydrated, and that doesn’t mean beer, people.”

Spoken with a truly fatherly tone. Which reminds us of the question that dogged Arroyo Seco Weekend when it was first announced: Would it be destined to go down as a “dad-rock” festival? And if so, would the family-friendly marketing, and the welcome mat clearly being laid out for The Oldsters, scare “sons” off? That didn’t ultimately seem to be a problem, as pretty much every ambulatory age range was well-represented on the festival grounds, with maybe the exception of free-range teenagers. There was definitely a difference between the two days, though (which were available as single-day tickets as well as packages): Things definitely skewed a bit older for the Petty-fronted Saturday bill, then trended younger for a Sunday lineup that had Mumford and Sons as headliner.

Weeks or months ago, you could hear music industry folk wondering if the festival art that portrayed a few dozen figurines gathered in front of a stage on an idyllic hillside might prove to be too prophetic, attendance-wise. But this was no first-year bust, like the ill-fated Rock in Rio festival in Las Vegas two years ago, where you could go hear some of the biggest acts in the world with all the elbow room in the world. Things did tend to be roomy around the second outdoor stage, where the contours of the crowds tended to exactly conform to the shade patterns formed by the trees on the west. But by late afternoon both days, it was a sea of bodies for the main stage, so that Sunday headliner Marcus Mumford almost didn’t seem to be kidding when he said to the crowd’s rear flanks, which extended beyond what would have been considered the main-stage field, “I thought you were all watching a different gig for a while. You’re watching our show!” (Goldenvoice didn’t release attendance figures; the city of Pasadena estimated ahead of time that the shows might attract 25,000 a day, a prediction that looked to these eyes to be extremely conservative.)

The artisan vibe included dozens of food vendors that tended toward high-end ma-and-pa restaurateur, with no unsightly chains in evidence… unless you’ve been to enough Coachellas or Stagecoaches that you think of the enduring Spicy Pie Pizza as a chain by now. There were a smaller number of the large-scale art installations Goldenvoice fests are famous for, most notably a red tube running down a dry water canal that everyone mistook for something functional until seeing signs that it was by the famous artist Doron Gazit.

As for what the extra cost of VIP tickets was good for, besides air-conditioned bathrooms? The chance to plop a low-slung beach chair or blanket under the oak trees in a fenced off area on the left side of the main stage field. Yes, the VIPs were essentially paying for shade — maybe a prescient perk in the age of global warming. (The general admission areas did offer some pleasant, oak-adjacent grassy knolls further away from the stage, for those fine with hearing but not seeing from a spot as picturesque as the poster art.)

For music fans who love classic R&B and jazz as well as rock, day 1 was an embarrassment of riches. The Preservation Hall Jazz Band commanded the main stage early on, and led a New Orleans-style line through the field at set’s end, while vibraphonist and fusion pioneer Roy Ayers and horn great Bernie Maupin, both 76, captivated smaller crowds in a tent. Jeff Goldblum got the tent to overflowing as he worked his comedy chops as well as his considerable piano skills with the ensemble he plays with in local jazz clubs — improvising a bossa nova instrumental of Petty’s “American Girl” for kicks. The soul meter went off the charts for William Bell, Charles Bradley, and the Meters, all paving the way for Saturday’s second-billed main stager Alabama Shakes, which has a serious soul stirrer in Brittany Howard, five decades the junior of some of the other acts on the bill.

For mainstream rock, day 1 had youngish festival favorite Dawes, the what-the-hell-are-they-doing-here ‘90s act Live, and of course Petty and the Heartbreakers, who seemed to have this as the only L.A. stop on their 40th anniversary tour until they announced a Hollywood Bowl show minutes after this set ended. “This one’s from 1982,” Petty said at one point, telling someone, “I know you weren’t there,” then adding to another front row fan, “You, sir, however, were there.” Maybe that’s a gag he pulls off every night, but it seemed especially well-suited to Arroyo Seco’s vision of creating a fest that’s all things to all ages while still being carefully curated.

The curation factor went down somewhat on day 2. What, you may ask, is young Andy Grammer, whose name has probably never appeared in the same sentence as the word “rock” before now, doing at what ostensibly seems, for all its jazz and soul sidebars, to be a rock festival? After his inch-deep set of deeply forgettable pop, we’re still not sure. You could almost ask a similar question of Fitz and the Tantrums, also undeniably a pop act, though their R&B inclinations ultimately proved they belong at least on the tangents of a throughline that ran through the festival.

What was clear, in any case — clearer than it was when you looked at the bill strictly on paper — was that day 2 was intended to be younger-skewing, with jazz tossed out of the tent in favor of jam-oriented bands, and pop acts like Rachel Platten getting more presence on the outdoor stages. That’s hardly to say that cred went out the window on Sunday, though: Neo-soul singer Alice Smith knocked it out of the very hot park early in the afternoon with her rendition of “I Put a Spell on You”; Lucas Nelson channeled both his dad, Willie, and more gravelly soul singers later in the day; and Galactic killed it with New Orleans funk (after being delayed for technical difficulties) as a less folksy alternative to Mumford at the end of the day.

Closing out the second stage, the Shins drew several times as large a crowd to that field as anyone else had — not surprising, given that they have a Greek headlining show coming up. They brought Los Lobos out for a collaborative effort — “They covered our song ‘The Fear’ and just destroyed our version,” James Mercer told the crowd — and, in honor of the previous night’s headliner, followed Jeff Goldblum’s lead in inserting an abbreviated version of “American Girl” into their set. Perhaps not surprisingly, hundreds of fans simply headed out to the parking lot after the Shins wrapped up rather than head over to see Mumford’s closing set, these being two bands with probably minimal fan overlap.

On the main stage, after Grammer and Fitz momentarily created some overlap with the KIIS-FM Jingle Ball vibe, Weezer brought it back to KROQ Weenie Roast territory… albeit perhaps creating some genre confusion when Rivers Cuomo and Brian Bell came out dressed as Axl Rose and Slash. There would be no such kidding around, of course, when Mumford and Sons closed the festival. Somewhat belying his folksy image, though, Marcus Mumford at one point threatened to come over and punch out “the wooded people” under the trees in the VIP section for daring to sit down while the vast field was SRO, but eventually added, “I was joking about coming over and f—ing shit up, though. I’m a long way from home. I could have, though.”

Hey, Mumford (and Sons) – leave them dads alone! If there’s a Utopian dream to this particular festival, it’s in at least pretending there’s no musical generation gap… an ideal that, for a couple of sweaty days, anyway, seemed surprisingly easy to believe.