As a child I remember playing a game in which one person made a repetitive mechanical movement, with a sound to match. The next person added a new movement and sound, and so on, until the participants had assembled a big, clanking, wheezing machine.
In this activity, the first player says one word, again and again, establishing a beat. (1, 2, 3, 4 --> The, The, The, The...) The next player adds a word and another rhythm. (1, rest, 3, 4 --> time, --, time, time) Each successive player builds the sentence and the sound.
When the composition is finished -- record it so you can play it back later.
There are many.
You can start by having the participants make a sentence, each person adding a word, then turning that sentence into music.
Or the words can be randomly chosen by the players on the fly.
The words/sentence can be related to a theme.
Each person can say a sentence, instead of just a word, and create a cacaphony of sentences.