The a cappella group Pentatonix is going to be back for their 3rd holiday special. "A Not So Silent Night" airs December 10th at 10p on NBC.They recorded in Las Vegas and include an all-star line up with illusionist Penn & Teller, Maren Morris, Backstreet Boys and Kelly Clarkson!The group just released a new album "Christmas Is Here!" Homeowners Threatened With $50k Fine For Extravagant Light DisplayBy Lori