Bringing people to their feet to sing a song joins everyone together and enables them to play a part in the funeral. The problem can be getting people to sing.
There are very few ‘traditional’ songs for non-religious funerals and, for this reason, favourite hymns are still popular. People don’t sing them for the words, they sing them because they have been singing them all their lives: they like the tunes. Abide With Me is still a funeral favourite, and The Lord’s My Shepherd. They seem somehow appropriate. Any religious people at the funeral will, of course, welcome this chance to voice their beliefs, so hymns serve a double purpose.
However, all sorts of secular songs are suitable too – especially songs from shows: You’ll Never Walk Alone, Somewhere Over The Rainbow. Most pop songs do not lend themselves to community singing, so make sure that whatever you like the sound of is singable by lots of people at the same time. James Blunt’s You’re Beautiful, for example, almost certainly wouldn’t work.