Following Tamar Braxton's exit, four couples draw closer to the Mirror Ball Trophy in "Dancing with the Stars" season 21 semifinals. For week 10, the contestants will have to knock out not one, not two but three routines – a first in the history of the long-running dance competition.

Last week, Alexa PenaVega went home after a shocking and dramatic elimination. With two pairs out on the same week, the semifinalists are now required to dance thrice. The first one is a dance these couples are yet to dance. The second one is a trio while the last one is a dance-off.

For the trio, the remaining "Dancing with the Stars" season 21 pairs will be joined by another pro dancer in the performance and they get the chance to choose which pro that was already eliminated from the season they feel will help them throw a great show.

Emma Slater will join Alek Skarlatos and Lindsay Arnold for an Argentine Tango. Karina Smirnoff returns to the stage to dance Samba with Carlos PenaVega and Witney Carson while Bindi Irwin and Derek Hough went with Mark Ballas for their Jazz routine. Nick Carter and Sharna Burgess chose Peta Murgatroyd for an undisclosed routine.

For the "Dancing with the Stars" season 21 semifinal dance-offs, Nick and Bindi will go head to head in a Samba routine while Alek and Carlos will battle it out in a Cha-Cha performance. The winners of the respective match-ups will be granted additional three points.

As for the individual dances, here is the complete rundown of the songs.

• Alek Skarlatos and Lindsay Arnold (Waltz) – "America the Beautiful" by Ray Chew Live
• Bindi Irwin and Derek Hough (Salsa) – "You're Never Fully Dressed Without a Smile" by Sia
• Carlos PenaVega and Witney Carson (Contemporary) – "Drag Me Down" by One Direction
• Nick Carter and Sharna Burgess (Tango) – "Scars" by Alesso featuring Ryan Tedder

The "Dancing with the Stars" season 21 semifinal airs Nov. 16 at 8 p.m. ET on ABC.