The winners of "The Sing-Off" so far are best seen as well as heard.

photo of Pentatonix

For me, The Sing-Off was the television singing competition. American Idol asked me to believe that these contestants would be, well, American idols, which they weren't, and while I love that moment of personal triumph in The Voice where someone sings well enough to make four stars turn around to hear more, there's no evidence that these voices' fame will significantly outlast the season. For the three seasons it was on the air, The Sing-Off didn't imply that the competing a cappella groups had great pop futures ahead of them. It simply presented them as good entertainment. The show was helped by the best crop of judges: Boyz II Men's Shawn Stockman was Randy Jackson-like in his wheel-of-catchphrases critiques, but Sara Bareilles and Ben Folds were far more precise and thoughtful in their comments, particularly Folds, who brought a producer's ear and an intelligent, witty kindness to the task.

The Sing-Off was missing from NBC's 2013 lineup and was presumed dead, but earlier this month the network announced that the show will return for the Christmas season with Jewel - a host and judge on Nashville Star - replacing Bareilles. The competitors will have to go a long way to top the season three winners, Pentatonix, who play the House of Blues Wednesday night. The five-voice group from Arlington, Texas had an appealing space in their sound, with much of the melodic content carried by founders Scott Hoying, Kirstie Maldonado, Mitch Grassi. They sang fluidly around the rhythm section of bass vocalist Avi Kaplan and beatboxer Kevin Olusola, whose tones effectively mimicked electronic dance music and give the group a contemporary sound that no one on the show approached with the exception of the sophisticated, jazz-oriented Afro Blue.

Grassi remembers the experience of the show. "It was intimidating because everybody was really, really good," he says. "Every week right before we performed, we thought, Oh my gosh. This is the week we're going to get kicked off. Because everybody was so good. The show taught us to put all our problems aside to not only arrange and perform the song, but to sort out our group thing and become a better musical entity." 

In Pentatonix' case, becoming a group didn't mean abstract team-building or bonding; it meant figuring each other out and how to work together. Hoying, Maldonado and Grassi had been together as a trio since high school, but they recruited Kaplan and Olusola to round out their lineup specifically for The Sing-Off. They didn't have months, much less years of experience together before they appeared on the show, so they had to learn how they worked together under the pressure of weekly television. Officially, contestants had a week to work out arrangements for each week's performance, but according to Grassi they really only had two or three days before they had to have something ready for camera blocking. "We were fortunate not to have this happen to us, but some groups would go out to show the producers their song, and the producers would say I don't like that. You have to change it," he says. "They would have to change to a completely different song in the middle of the week." As nerve-wracking as it could be, it also taught them to hone in on a song and arrange quickly. "We did our arrangement for 'Pusher Love Girl' in two days, which is wild," Grassi says.

The Justin Timberlake song is just one of the hits of the day that Pentatonix covers on its YouTube channel, most garnering millions of views. The channel was part of a conscious effort to let people know the group still existed and remained active after The Sing-Off, but it began organically when someone shot them singing Maroon 5's "Moves Like Jagger" in a living room. "Most reality show winners, if they don't do anything within an allotted time, people forget about them," Grassi says. "We really didn't want that to happen, so we wanted to be always always coming out with something new. And, keep our fans engaged at the same time." 

The YouTube videos are endearingly goofy - there's no getting around it - but the creativity and talent is undeniable. The "Evolution of Music" medley moves from 11th Century spiritual music to Carly Rae Jepsen in four minutes, and it has racked up 14 million views in three months, while versions of Macklemore and Ryan Lewis' "Thrift Shop" and Psy's "Gangnam Style" have each passed eight million views. Hoying had to learn the lyrics to "Gangnam Style" phonetically, but he memorized them in a few hours and though Pentatonix hasn't played the song live in a while, Grassi says it can.

Pentatonix benefits from being seen, whether on television, video or live. As an audio-only experience, the group remains enjoyable, but the spectacle of the rhythm section creating synth-like sounds with its voices is lost, and the songs can be mis-heard as three vocalists over electronic tracks. Grassi is the electronic music fan in the group. "Kevin hears a lot of music through me," he says. "But every single member of the band has wildly different musical interests, which I think is awesome. We're not limited to one genre. We can explore whatever we want. Electronic music is definitely an influence."

As part of its prize for winning The Sing-Off, Pentatonix won a recording contract with Sony, but the group left the label to cut PTX Volume 1 for the independent Madison Gate Records. Grassi speaks well of Sony, but says "the one we're on now gets us better." The EP was released last month and includes a cappella covers of Nicki Minaj, fun., and Goyte, along with two new songs. Those two songs took the longest to record because the members are singers first. "We aren't trained songwriters, so we don't know what direction to go in or how to start," Grassi says. Original songs put the band in a tricky spot. They don't want to be seen as a novelty group that makes different sounds with their mouths, "but it is what sets us apart," he says. Similarly, since The Sing-Off, Pentatonix is known for rearranging pop songs as a cappella performance. New songs may be necessary to stave off another  novelty charge, but they're not what the fans are coming for.

"Earlier in our careers, we wanted to be mainstream," Grassi says. "I'm not sure if that's a big goal of ours, but we still want to be known as much as we possibly can. Our material is pretty accessible, but we don't just write it to write it. It's as artistic as we can make it."