A couple of months ago, the Mormon Tabernacle Choir invited people to
sing the Hallelujah Chorus and submit it through YouTube to be part of a virtual choir performance.
Over a thousand videos were submitted, and they are blended in this
video with the choir. Those who wished to sing were instructed to post
their videos on YouTube with the hashtag #Hallelujah. You can see quite a variety of participants there, or go here to see an interesting selection of submissions.