Concert review: Pentatonix at Prudential Center

“I can’t believe there are this many people here for an a cappella group,” said Avi Kaplan of Pentatonix, looking out over an audience of thousands at the Prudential Center in Newark, Thursday night. Later in the evening, group member Mitch Grassi pronounced it “so surreal” that so many people were there.

Tom Brenner/Prudential Center Pentatonix performing Thursday night at the Prudential Center.

Pentatonix is an a cappella group, and it’s not exactly a common thing – perhaps it is even, in fact, unprecedented – for an a cappella group to achieve arena-filling popularity. But Pentatonix, a five-piece group originally formed in Arlington, Texas – whose members are now all in their mid- to late-20s – has done it. And they’ve done it in a very modern way. They won the third season of the television competition series “The Sing-Off” in 2011, but even more crucially, have become one of the most popular groups ever on YouTube; the videos on their PTXofficial channel have received more than 1.8 billion views, and the channel has more than 11.5 million subscribers.

They write much of their own material, but it was still the novelty songs and covers that made the biggest impressions at the Prudential Center, particularly medleys of songs by Michael Jackson and Daft Punk, and a version of Bach’s Cello Suite No. 1 Prelude for which Kevin Olusola both played cello and accompanied himself with beatboxing (i.e., making percussive noises, vocally).

Opening act Us the Duo returned to expand the quintet to a septet for a cover of Dolly Parton’s “Jolene,” and the set ended with a soaring, earnest version of Leonard Cohen’s “Hallelujah” — dedicated to Cohen, whose death, at the age of 82, was announced shortly before Pentatonix took the stage.

Many of the covers, though, were of more recent vintage, including Kiiara’s “Gold,” Meghan Trainor’s “No,” OMI’s “Cheerleader” and a medley of Imagine Dragon’s “Radioactive,” A Great Big World’s “Say Something” and Stromae’s “Papaoutai.”

Throughout the show, the between-song commentary was brief and bland – the kind of well-rehearsed things a musician will probably say every night, the same way, on a long tour (Pentatonix has been on the road, pretty much nonstop, since April). There was a nice bit of audience bonding on “Misbehavin’,” though, when group members invited five fans to come onstage and sit on bean bag chairs with them, and sing along.

Some videos were shown, and there was a burst of confetti during the last encore, “Sing,” But visually, it was not a particularly elaborate show, by arena-tour standards. The emphasis was almost always on the rich vocal blend these five are able to achieve, with, most typically, tenor Grassi, baritone Scott Hoying or mezzo-soprano Kristin Maldonado taking the lead, bass Kaplan and beatboxer Olusola anchoring the arrangements, and Olusola also stomping out beats with his feet.

There were two opening acts.

Abi Ann took the stage first. She was impressively poised for a 19-year-old. And while she mostly sang songs that would fit right in on pop-oriented Top 40 stations, she branched out, surprisingly, to country with “Truck Candy,” in which she asserted that she doesn’t want to just be a guy’s truck candy (i.e., arm candy for a guy driving a truck).

Up next were Us the Duo – the husband-and-wife team of Michael and Carissa Alvarado. And they showed even more range in their set, which included everything from a jazzy, sultry remake of The Beatles’ “Can’t Buy Me Love” to “ ‘Til the Morning Comes,” a song that Carissa Alvarado said was inspired by Johnny Cash and June Carter Cash, and borrowed its melody from Johnny Cash’s “Folsom Prison Blues.”

“No Matter Where You Are,” which they said they co-wrote for their wedding, was a sentimental highlight, and their closing song was gimmicky, but fun: A whirlwind medley of recent pop hits, including Adele’s “Hello,” Taylor Swift’s “Bad Blood,” Nick Jonas’ “Jealous,” The Weeknd’s “I Can’t Feel My Face” and many others.