After their longest season yet, it was down to a college a cappella group, a hip hop group and a group creating an electronic dance club sound on the season finale of 'The Sing-Off' (Mon., 8PM ET on NBC). It was amazing watching these three powerhouse groups through the season.

!!SPOILER ALERT!!

The Dartmouth Aires soared under the powerful lead vocals of Michael, while it took Urban Method a little while to find their strengths beyond their rap niche. Pentatonix struggled a bit with deciding how far to take their signature remixes. But all three groups excelled and impressed week after week.

Youthful a cappella group Pentatonix gave it their all and wowed the crowd on 'The Sing-Off' (Mon., 8PM ET on NBC) last night.

The Los Angeles-based group performed their unique take on Katy Perry's song 'E.T.' and afterward seemed real happy with how it went.

Judge Sara Bareilles told the singers how she loved that each member of the group "had your little moment in that song where you just go to shine and to sparkle and we got to see all the dimensions of you."