HoagieNation finally made it to the Mann Center on Saturday with a Hall & Oates-headlined lineup opening a late, fingers-crossed start to music festival season in Philadelphia with a slate of feel-good bands that provided an upbeat respite from a pandemic that seems as if it will never end.

From the Philly-bred rock-and-soul duo on top of the bill down through British pop-rock band Squeeze, R&B crowd-pleasers Kool & the Gang (who played on despite the death of a founding member earlier in the day), reggae stalwarts the Wailers and “Expressway to Your Heart” Philly soul purveyors Soul Survivors, it was a sultry late summer’s day and night of hits, hits and more hits.

“This is our second show back in the world, and what a place for it to be,” Daryl Hall told the crowd of more than 10,000 at the fest, which drew an interracial, mostly middle-aged and maskless audience to the Fairmount Park open-air amphitheater complex.

“I’m so happy to see you guys,” said the singer for the band that he and John Oates formed after meeting in West Philly’s Adelphi Ballroom in 1967. “It’s been a hard year. What the hell happened? And continues to happen.”

After debuting at the Festival Pier on Penn’s Landing in 2017 and 2018, HoagieNation took the next year off after that venue fell victim to real estate developers. A planned move to the Mann last summer was prevented by the coronavirus shutdown.

The Philly fete’s successful staging on Saturday — even as the delta variant of the virus has fueled a surge, with the U.S. now averaging more than 100,000 new infections a day — struck a note of cautious optimism. Maybe if safety protocols are closely followed and we all go out and get vaccinated — as WMMR-FM (93.3) DJ Pierre Robert urged everyone to do before H&O’s set — we can still have nice things.

HoagieNation loves to Philly it up. Craig Robinson, the comic actor and musician who performed on the Mann’s Skyline Stage with his funk band the Nasty Delicious, not only included “Gonna Fly Now (Theme From Rocky),” the proudly pandering spokesperson for cold cuts company — and festival sponsor — Dietz & Watson also was accompanied by Eagles cheerleaders and the team’s yellow-beaked mascot, Swoop.

Selfies were taken with a Ben Franklin impersonator, and people posed against a wall between images of a hoagie roll, happy to play the role of meat and cheese. On “Get Down on It,” Kool & the Gang was joined by ingratiating Flyers mascot Gritty busting ungainly moves.

Before the music started, there was a “Hoagie Happy Hour,” during which free samples from shops around the region were passed out. (Though it must be said that if you missed those giveaways, hoagies were weirdly hard to find at the festival at large. I went for a tasty pulled pork and mac & cheese from the Farmstead Foods truck.)

Kool & the Gang was preceded by a warm-up set by DJ Prince Hakim, who asked for a moment of silence for saxophonist Dennis “D.T.” Thomas, who died in his sleep in Montclair, N.J., at age 70 earlier Saturday. (He last played with the band in July and was not scheduled to perform at the Mann.)

Considering those circumstances, the band’s hour-long set was a breezy, seemingly carefree celebration. It came to a sing-along conclusion, of course, with “Celebrate” but also engaged the crowd with equally irresistible songs such as “Jungle Boogie” and “Hollywood Swinging.” The sloping lawn of the Skyline Stage became a shake-off-the-COVID-cobwebs dance floor.

Bassist Robert “Kool” Bell was the only original member of the band in the current K&TG lineup, a similar distinction for the Wailers’ bassist Aston “Familyman” Barrett. The reggae band played before Kool & the Gang on the Mann’s main stage. “Familyman” lives up to his name by employing his son Aston Jr. on drums and cousin Josh David Barrett on vocals, as well as ace guitarist Donald Kinsey.

When it comes to such songs as “Get Up, Stand Up,” “Could You Be Loved” and “Stir It Up,” it would be preferable to hear the late Bob Marley himself sing them, but he’s been gone 40 years. These Wailers may resemble a cover band of the highest order, but their feelin’ irie optimism played wonderfully well under the roof of the Mann’s capacious TD Pavilion, with weed smoke floating in the breeze.

Immediately preceding Hall & Oates were Squeeze, led by New Wave-era Brit songsmiths Glenn Tilbrook and Chris Difford, whose way with an inviting melody and witty turn of phrase led to many Lennon and McCartney comparisons back in their day.

On Saturday, the man bun-sporting Tilbrook dared to make the uncool rock fashion faux pas of wearing short pants on stage, and led the sharp seven-piece band through a winning set full of ear worms: “Pulling Mussels From a Shell,” Tempted,” “If I Didn’t Love You,” and “Black Coffee in Bed.” Surprise: Philadelphian Owen Biddle, formerly with the Roots, is now the band’s bass player.

Hall & Oates opened with the catchy if also mean-spirited “Maneater” (“Watch out boys, she’ll chew you up”). Their satisfying get-up-out-of-your-chair, 90-minute set drew from a seemingly unending series of ‘70s and ‘80s smash hits, with soft-rock subtlety melded with Philly and Motown soul.

An elegant “Sarah Smile” began with Hall on solo piano before Oates entered on guitar and the full band gracefully joined in. “She’s Gone” built to a soaring emotional crescendo; at 74, Hall remains remarkably undiminished as a vocalist.

For fans singing along, the joy of live music was regained, at least for one Philly proud day in Fairmount Park.