The Sing-Off

The show featured eight a cappella groups performing popular songs live. The winner's prize was $100,000 and a Sony Music recording contract.[2]

The first episode saw all groups perform their signature song. The second episode saw the remaining six groups perform two songs: in the first half of the show, each group performed one big hit from recent years; and in the second half, each group sang one "guilty pleasure" song. The third episode had the five remaining groups perform a medley from a classic artist. In the second part of the show, the four remaining groups performed songs that the judges picked specifically to showcase each group's strengths.

At the end of the third show, viewers were asked to call or text to vote for one of the remaining groups, Voices of Lee, The Beelzebubs, and Nota. The group with the most votes was revealed in the finale, and in the end Voices of Lee was revealed to come in third place halfway through the finale, with Nota being declared winners.

In the second season, the show returned on December 6, 2010, for five episodes, with the number of groups increased from eight to ten. Nick Lachey returned as host for the second season, as well as the three judges Ben Folds, Shawn Stockman and Nicole Scherzinger.

The first episode had the groups sing their signature songs. In the second episode, the remaining eight groups sang a modern song that was released in the past five years. For the third episode, the groups covered a rock song and a "guilty pleasure" piece. The fourth episode was to sing a medley of songs by a noteworthy artist and perform a song chosen by the judges. One more group was supposed to be eliminated, but the judges chose to put Jerry Lawson and The Talk of the Town, The Backbeats, Street Corner Symphony, and Committed all through to the finale. This is the only season to have four groups in the finale.

At the finale, Jerry Lawson and The Talk of the Town was the first to be eliminated. The Backbeats came in third place, Street Corner Symphony came in second, and Committed won the title.

Sara Bareilles was a new judge for the third season, replacing Nicole Scherzinger

The Sing-Off was renewed for a third season of eleven episodes and premiered on September 19, 2011.[7] This was the first Sing-Off season to include sixteen groups of a cappella singers. On May 16, 2011, it was announced that judge Nicole Scherzinger would not return for this season due to her commitment duties as one of the judges of The X Factor,[10] and that Sara Bareilles would replace Scherzinger on the judging panel. Nick Lachey, Ben Folds, and Shawn Stockman all returned.[11][12]

Since there were sixteen vocal groups, the groups were divided into two brackets of eight for the first four episodes to get down to the top ten. The first and second episodes had the groups sing their signature songs, while the third and fourth episodes had the groups perform a current hit and a classic from the 1960s. The fifth episode saw the two brackets merge, with the remaining ten groups performing their guilty pleasure songs. In the sixth episode, the eight remaining groups performed a hip-hop song and at the end of the episode, the show had its first-ever Sing-Off showdown, in which bottom two groups sang different versions of a song and the judges voted which to send home. The remaining groups in the seventh episode sang a superstar medley and in the eighth episode, the remaining six performed a country song and a rock-and-roll song. The top five groups performed rhythm-and-blues hits from today, and classics from the past, in the ninth episode. In the tenth episode, the top four performed master mix songs, a song picked by the judges. In the elimination, Urban Method and Pentatonix advanced to the finale. The judges could not come to a decision on the remaining two groups, Afro-Blue and the Dartmouth Aires, so they performed their favorite songs from past performances. In a two-to-one decision by the judges, Afro-Blue was voted off and the Dartmouth Aires advanced to the finale. The live finale crowned Pentatonix as winners, with the Dartmouth Aires coming in second, and Urban Method coming in third place.

One week after the third season ended, a Christmas special (titled "The Sing-Off Christmas") was aired on December 5, 2011. It featured groups from all three seasons singing various Christmas songs.

Jewel was the new judge for the fourth season, replacing Sara Bareilles

On March 13, 2013, NBC announced that The Sing-Off would return for a fourth season, with additional production by Mark Burnett's One Three Media, which also produces NBC's other singing competition show, The Voice.[13] After the fourth season was announced, Sara Bareilles announced that she would not be returning to the show.[14] On July 2, 2013, it was announced that Jewel would replace Bareilles as a judge.[3]

As a new addition to the season, at the end of every show, the bottom two groups decided by the judges faced off in an "Ultimate Sing-Off", with each group singing the same song trying to eliminate their opponent.[15] The show returned on December 9, 2013, and aired over several nights, concluding on December 23, 2013.[1] In a first for The Sing-Off, groups from the show will go on tour, with 32 shows scheduled in 32 cities during February and March 2014.[16]

Home Free was crowned the winner, with Ten coming in second and Vocal Rush coming in third.

Patrick Stump was the new judge for the fifth season, replacing Ben Folds

On October 1, 2014, NBC renewed the series for a fifth season to air at the end of 2014.[9] Although a "season" of shows did not air (to the confusion of some fans), NBC aired a two-hour special on December 17, 2014. Lachey, Stockman and Jewel returned with Patrick Stump replacing Folds, and Deke Sharon returned as music director/vocal producer.[17]

At the end of the night, the Vanderbilt Melodores were crowned as the new champions, The Exchange were the runners-up, and Traces placed third. The other competitors on Season 5 were a.squared, San Fran 6, and Timothy's Gift.

Season 5 marked the first and only time that a competing group on the show was permitted to use electronics to supplement their live vocal sound (as demonstrated by a.squared's performance of "Pompeii" by Bastille). This use of electronic effects had been previously banned, most notably in the case of season 3 contestants Arora (formerly Sonos) who were not allowed to perform with their signature effects pedals.

The special received 5.10 million viewers, a 1.3 rating, and a 4 share.[18]