Brace yourself for a singing showdown as 30 of the UK's most exciting groups face-off in an a cappella contest based on sheer vocal talent. Cat Deeley hosts. We’re ...

Brace yourself for a singing showdown as 30 of the UK's most exciting groups face-off in an a cappella contest based on sheer vocal talent. Cat Deeley hosts. We’re ...

It’s unclear, however, what caused the apparent issue that prompted Underwood to sing a cappella. You can watch the full moment in the video player above. Carrie Underwood performs during the ...