This might be called a 'disappearing' and 'reappearing' song. It is a lot of fun, but is best sung in a fairly quiet spot, where there are no distracting noises.
Many different songs can be used, but the most common is 'John Brown's Body'. In case you don't know the words of the chorus, here they are:
John Brown's body lies a mould'ring in the grave,
Everybody sings this through together. Then they sing it through again, this time leaving out the last word of each line:
John Brown's body lies a mould'ring in the ____
but singing the last line complete.
The next time through, they omit 'the', and then, in successive choruses, 'in', 'mould'ring', 'a', 'lies' and so on.
It is important that the gaps are left as pauses, so that the song takes the same length of time on every occasion.
At last, they will be left with just the final line, and a long period of silence before it. This is where a good sense of rhythm and timing really counts! What usually happens is that the singers launch into 'But his soul goes marching on' in ragged disarray.
The next stage is to bring back John Brown. This is done by building up the lines backwards, from the end of each line. They start off with: