It was hosted by Nick Lachey (from the boy band 98 Degrees), with judges Ben Folds, Shawn Stockman (of the rhythm-and-blues vocal group Boyz II Men), and originally Nicole Scherzinger, later replaced by Sara Bareilles.

A cappella groups from the United States, including Puerto Rico, were chosen by audition and advanced in the competition based on judges' eliminations.

The program has featured guest appearances by various popular artists, including Bobby McFerrin, Natasha Bedingfield, Jay Sean, Smokey Robinson, Neil Diamond, Boyz II Men, Flo Rida and Sara Bareilles.

[7] Unlike previous seasons, the early start in September allowed for the production of more episodes and the number of participant groups increased.

[8] However, on March 13, 2013, almost a year after the show was not renewed, NBC announced that The Sing-Off would return for a fourth season.

[1] On December 17, 2014, NBC aired a special two-hour episode of The Sing-Off, billed as "Season 5" of the show.

The special was filmed at the Dolby Theatre in Los Angeles and featured six competing groups, with the Vanderbilt Melodores being crowned the champions.

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.

Nick Lachey returned as host for the second season, as well as the three judges Ben Folds, Shawn Stockman and Nicole Scherzinger.

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.

The fifth episode saw the two brackets merge, with the remaining ten groups performing their guilty pleasure songs.

The top five groups performed rhythm-and-blues hits from today, and classics from the past, in the ninth episode.

[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.

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).