When Phantogram played its last of nine — yep, nine — performances in five days at the South by Southwest Music Conference last month, the setting seemed all too perfect: the rooftop of a parking garage six stories above the fray, amid the fast-rising skyline of Austin, Texas.

“Good thing we don’t have vertigo,” singer Sarah Barthel said later.

Even without the extra 60 feet beneath them, Barthel’s electronica-fied synth-rock group had already elevated its live act, with a vibrant light show and electric energy to go with the more kinetic, eruptive, harder-hitting songs on the long-awaited sophomore album, “Voices.” The record arrived in February almost four years after the release of Phantogram’s debut.

Much of what happened in the interim led to the heavier, fuller, bloodier sound on “Voices,” Barthel said in a phone interview after SXSW.

“We wound up doing about three years of touring for the first album — and learned a lot along the way,” the singer said, sounding bubblier and more outgoing in conversation than her darkly angelic, coolly detached, cooing voice suggests on record. She and guitarist/singer Josh Carter are the creative duo behind the band, which expands to a quartet in concert.

“After all that touring, we realized we wanted a heavier sound — more bombastic, more live drums and louder dynamics. Those are things we never knew about for our first album because we wrote it before we started touring. And, of course, we had more budget and resources to work with this time.”

“Voices” was issued by Universal’s Republic Records, one of many labels that pursued the group after its haunting 2010 single “Mouthful of Diamonds” took off. While the record deal added to the length between albums — “Voices” was actually finished last June, Barthel said — it seems to be paying off in added exposure.

Headed to Minneapolis for a sold-out First Avenue show Sunday, the band has already played late-night gigs with Letterman and Kimmel and earned numerous upcoming festival gigs, including Lollapalooza. Locally, the throb-poppy second single “Fall in Love” recently topped 89.3 the Current’s chart, and the moodier, rockier cut “Black Out Days” also got heavy airplay.

Barthel said the major-label deal in no way influenced the making of the new record, save for the extra time and doodads it afforded them.

“We were able to get into a real studio and use an immense amount of instruments, from really cool analog synthesizers to guitar pedals we’d never used,” she recalled. “It was a lot of experimenting.”

From a small town to Big Boi

Even though Phantogram has one of the more distinctive sounds among bands using electronic drums and samples, Barthel said they are careful to make sure their sonic adventurism never gets in the way of the songwriting.

She and Carter share the writing duties equally. The new album also finds him stepping up to handle a quarter of the vocal work.

“When we were writing ‘Voices,’ we stripped down every song and played versions of them on the piano,” she said. “We get real excited being able to add those production elements — they go hand in hand with the way we write — but we definitely make sure the songs will still stand up without all that.”

Natives of Greenwich, N.Y. (near Saratoga Springs), Barthel and Carter have been friends since junior high school. “Josh always says we’re psychic twins,” she said.

They didn’t start making music together until they were in their early 20s. Their goal then, Barthel laughingly recounted, was “always to move down to the city [New York] and be part of some cool scene there.

“Instead, we actually both wound up living up at Josh’s parents’ house during the writing of the first album. Looking back, though, it was great for us, because there wasn’t a scene to follow or trends or anyone really guiding us besides ourselves.”

One seemingly unlikely supporter who took note of their unique sound was Atlanta hip-hop legend Big Boi. The OutKast co-founder enlisted Carter and Barthel as collaborators for three tracks on his acclaimed 2012 album “Vicious Lies and Dangerous Rumors.”

“He started tweeting about us, and it went from there,” Barthel explained. “We just totally hit it off the first time we met. Josh had a big cache of beats he wanted to show him, so he ended up flying us down to Atlanta to work at Stankonia Studios. He really became a mentor to us and now considers us a part of the Dungeon Family.”

Pointing back to the story about wanting to move to New York City, she joked, “So who’s cool now?”