The Nick Lachey-hosted show welcomed groups Dartmouth Aires, The Collective, Messiah's Men, Pentatonix, Sonos, Soul'd Out, North Shore and Deltones to the stage, as they all attempted to impress judges Ben Folds, Shawn Stockman and Sara Bareilles.
Watch the group performance of 'Sing' below:
As with last week's season premiere, the eight groups took to the stage in two brackets of four, with one group in each bracket being sent home.
Unfortunately for gospel, Afro-centric and soul group Messiah's Men and high schoolers Soul'd Out, their Sing-Off journey came to an end following their performances, meaning they lost the chance to win the $200,000 prize and Sony Music recording contract.
Messiah's Men escaped the danger of civil unrest in Liberia and now reside in Minneapolis. They began singing together in the refugee camps in Liberia and said in their pre-performance video it's important for them to retain their connection to the country. They said they felt "blessed and privileged" to have been given the opportunity to perform on The Sing-Off stage and tell their story.
They chose 'People Get Ready' by Curtis Mayfield as their song - performing in the same bracket as Dartmouth Aires, Pentatonix and Sonos - and all three judges praised their unity and the powerful performance. Shawn said he could feel all of their influences and pointed out songs can be a "spiritual elixir" even in the worst of times.
However, minor critiques included trouble staying on key and wavering tone and they were sent home over Sonos. They chose 'Sweet Low, Sweet Chariot' as their swansong.
Watch Messiah's Men's performance below:
High school group Soul'd Out were the biggest and youngest group in the competition this season and described themselves as the real-life version of Glee. They said taking part in the show was particularly poignant for them because ten of them are graduating this year and it would mark the last time they got to perform together.
They chose 'Aquarius/Let The Sunshine In' from Hair for their song, which the judges recognised was a tough choice because of its intricacy. Shawn said, however, that they held their own and captured the essence, while Sara said she loved seeing big dreams from small towns and praised their infectious energy, emotion and maturity.
Ben agreed they did really well considering their age but thought they fell apart slightly in the second half, while Sara thought some of their chords became muddled and they became the fourth group to leave this season.
Soul'd Out chose 'Mama I'm Coming Home' as their swansong.
Watch Soul'd Out's performance below:
The rest of the six a cappella groups who performed all made it through to the next stage. Watch videos of each of their performances below:
Dartmouth Aires - 'Higher Ground' by Stevie Wonder
Pentatonix - 'E.T.' by Katy Perry
Sonos - 'Wicked Game' by Chris Isaak
The Collective - 'Rolling in The Deep' by Adele
The Deltones - 'Feels Like Home' by Randy Newman
North Shore - 'Runaround Sue' by Dion
The Sing-Off airs Mondays at 8/7c on NBC