The first season of The Sing-Off premiered on December 14, 2009. The show featured eight a cappella ...
The second season of The Sing-Off premiered on December 6, 2010. The number of a cappella groups was...
The third season of The Sing-Off premiered on September 19, 2011. The number of a cappella groups wa...
The fourth season of The Sing-Off returned with the number of a cappella groups competing decreased ...