Congregation

We think that congregational singing at civil
ceremonies is usually a bad idea, because...

1. The only possible 'congregational' music permitted at a civil ceremony is pop, jazz or folk – all of which are usually performed by a solo singer and are therefore not sung metrically. In other words, unlike hymn-tunes, the melodies don’t have strict, regular timing so it’s hard for guests to sing together, as they won’t all know exactly when they’re supposed to sing.
2. There are very few tunes that are permissible for use at a civil ceremony which will be known to guests of all ages.
3. The British are very unwilling singers in formal situations anyway.

If you are determined to make your guests sing at the ceremony, the best way to achieve this is to engage professional singers to perform the song, and to encourage your guests to join in with them.