A few of them cried after it was all over.
The Missing People Choir performed for the Britain's Got Talent television show which was broadcast on Saturday.
Among the members of the choir was Denise Horvath-Allan whose son Charles Horvath went missing in Kelowna on May 26, 1989. He is believed to have been murdered.
Horvath, a British national, was 20 years old when he vanished without a trace while staying at Tiny Town campground on Lakeshore Drive. He was hitchhiking and working his way across Canada to connect with Canadian family members.
Denise Horvath-Allan is one of the driving forces behind the choir, which has become another way to bring attention to the plight of families suffering through the pain of a lost loved one.
Images of some of those missing were flashed up on a screen during the performance.
The choir performed "I Miss You' during its audition.