'Pentatonix' has brought a cappella music back to the mainstream of American music culture. Their renditions of popular songs are free of any instruments. The group captures the essence of each song with just their voices.

Musical performance group on stage in a concert setting, with adults wearing formal attire under blue-toned starry night sky effects.

In this performance video of Leonard Cohen's 'Hallelujah' the crowd starts to cheer, and the lights fade in slowly as the song begins. There's a new lead singer with each verse.

They stand on a staircase on stage while the background is lit with stars. The group is wearing flashy and fancy clothes. The lights start to move as the beat-boxing comes in on the chorus and the song gets more intense.

A concert scene at an indoor venue with a starry sky effect above; audience in silhouette holding up phones or cameras to capture the performance.

Cohen's 'Hallelujah' has been covered by some of the most famous musicians and vocalists in the world. Bob Dylan, Willie Nelson, and Justin Timberlake all performed their own version of the song.

The song itself was written by Canadian singer Leonard Cohen, originally released on his album 'Various Positions' in 1984. It achieved little success until it was recorded by John Cale and later by Jeff Buckley.

An indoor stage setting with a musical performance group in formal attire during what appears to be an evening event under artificial lighting.

'Pentatonix' was formed in 2011 and won the third season of NBCs' The Sing-Off.' They received a recording contract, and they have swept the nation ever since. After releasing multi-platinum albums, 'Pentatonix' has become a musical force of nature!