For younger children, I can see using the song Deep and Wide where you take out one word out each round and then put them back in one round at a time and then talk about how it's harder to sing the more words that are "lost" and much easier to sing when they are all "found"

1st round:
Deep and Wide
Deep and Wide
There's a fountain flowing 
Deep and Wide

2nd round:  Take out Deep
MMM and Wide
MMM and Wide
There's a fountain flowing 
MMM and Wide

3rd round: Take out deep and wide
MMM and MMM
MMM and MMM
There's a fountain flowing 
MMM and MMM

and so on. . .