The Hard Rock Café on the Strip, Dec. 15

The self-proclaimed “choir nerds” and Season 3 winners of NBC’s The Sing-Off are an a cappella group of five vocalists who create their own beats, sounds and harmonies. Using nothing more than their voices, Pentatonix remix and re-create current hits and old favorites.

The group smoothly, then passionately performed Florence + the Machine’s “Dog Days Are Over” and mashed-up Justin Beiber’s “As Long as You Love Me” with Katy Perry’s “Wide Awake.” The show’s high point happened when Pentatonix invited a young lady named Dorothy to the stage, sat her down in a chair and serenaded her to the Marvin Gaye classic “Let’s Get it On.” They mixed her name into the lyrics while giving her a four-way lap dance, much to Dorothy’s (and the audience’s) bashful approval.

A medley (which included “Call Me Maybe” by Carly Rae Jepsen, “We Are Young” by Fun. and “Somebody That I Used to Know” by Making Mirrors) kept the audience singing along before the group brought holiday cheer with a moving performance of “Angels We Have Heard on High.” ★★★★☆