iHeartRadio 2012: No Doubt, Rihanna, Usher Rock Vegas on Day 1

Music Photos of the Year 2012

September 21: Gwen Stefani of No Doubt and Pink perform onstage during the 2012 iHeartRadio Music Festival.

"Go ahead and stare / and take a picture please / if you need,"and Demi Lovato, on separate occasions, as well as Olympian Ryan Lochte) and a giant onstage wall of photos and tweets posted and updated throughout the night, it was hard to walk away from the event (or turn it off on the various streaming platforms or hundreds of Clear Channel stations that broadcast the event live) without feeling just a brush of the zeitgeist - albeit twinged with nostalgia.

VIDEOS: Billboard @ iHeartRadio Music Festival

Those acts shared the stage with veterans like Bon Jovi, who played a hits heavy 30-minute set that included faves like "Wanted Dead Or Alive" and "Bed Of Roses," as well as Green Day, who also have an album out Tuesday, whose set was cut short due to a teleprompter informing the band they had one minute left in what was barely a 20-minute set. It did not end well.

Watch Green Day Smash Their Guitars, Storm Off at IHeartRadio

Further proof of this mix of nostalgia and now-ness arrived later on in No Doubt's performance when P!nk, who happens to open Day 2 on Saturday, appeared to perform a surprise duet of the band's breakthrough hit "Just A Girl." Though the moment was a years-in-the-making opportunity for two of the 2000s' leading radio divas to finally share a stage, it had a uniquely 2012 feel to it. At one point, P!nk dropped to the floor in push-ups -- a seeming bid to compete with the impressively fit Stefani, who at 42 still looked and sounded like the 25-year-old holding an orange on the cover of the "Tragic Kingdom" CD booklet wedged into tens of millions of Jewel Case sleeves these days.

Elsewhere, country fans got a healthy dose of three chart-topping acts -- Aldean, Miranda Lambert and the latter's side project the Pistol Annies, who joined the singer halfway through her early, energetic set. Having just kicked off their first headlining tour last week in New York, the gig was only the band's third on this tour -- a refreshing sign that Lambert was happy to share the spotlight with her collaborators despite a white-hot solo career that currently includes "Fastest Girl In Town," which re-entered the Country Songs chart this week at No. 11 following the singer's performance on the Canadian Country Music Awards.

EDM fans got a taste of a weekend lineup that also includes Calvin Harris and Deadmau5 when Swedish House Mafia showed up toward the night's fourth hour to spin a couple tracks from the back of the arena -- before dimming the lights to make a special announcement. "We're about to play a song live for the first time," the DJ trio announced, as blue lasers shone upon the main stage. Within seconds, the opening keyboard lines started to play from "Euphoria," one of two collaborations from Usher's "Looking 4 Myself" -- which sure enough summoned the singer himself to take the lead on the throbbing house-pop track while the DJ booth slowly dimmed its lights.

Usher arguably took home the night's hardest-working performer award -- dancing, belting and sweating his way through a dance-intensive, ballad-light set that had the crowd on its feet for nearly its entirety, from "Yeah" to "DJ Got Us Fallin In Love Again" to current single "Scream" and David Guetta collab "Without You." He could only raise a high bar for the night's closer, Rihanna, who nevertheless performed virtually all of her hits from "Umbrella" onward and reprised the Egyptian set from her MTV Video Music Awards performance earlier this month. Just as she put choreography before vocals at times at the VMAs, Rihanna's set was heavy on spectacle where it was light on live vocals -- though, to the singer's credit, she picked up the slack during the set's second half as she sang a medley of hooks she's performed on hip-hop hits (T.I.'s "Live Your Life," Jay-Z's "Run This Town," Kanye West's "All Of The Lights") and her own "Don't Stop The Music," where she forgot a few words but at least won the crowd over with her energetic attempts.

It's worth noting, however, that Rihanna did not debut or hint at any new material coming this year -- despite reports last week that the singer was preparing a seventh (!) studio album for release in November, which would be her fourth in the last four years alone. Instead, the singer appeared to be previewing her upcoming Diamonds tour, by sticking to six of her Talk That Talk album's seven singles -- including a medley of "Cockiness (Persuasion)" and "Birthday Cake" that was tellingly filmed by Clear Channel's cameras from the waist up for the venue.