I learned this game at Kani Club, the theater improvisation group in Tokyo, Japan. The game asks participants to filter their free association through their sense of what others might say. The object is to avoid "idiocy" -- in the sense of being isolated in one's thinking. At the same time, the "idiotic" answers are often reasonable or creative.
The joker chooses a category, for example, "Paris, France" and the players think of something most people would associate with that category (Eiffel Tower, Arc de Triomphe, baguette, Edith Piaf, etc.), keeping their answers to themselves for the moment.
When everyone has an answer, the joker says, "Paris, France. Three, two, one..." And, on zero, everyone calls out their answers simultaneously. They keep calling out their answers, moving around the room seeking others with the same answer. When they find them, they stand next to each other, calling out their answer, until all have found their partners (or determined that they are alone).
The joker then asks groups to give their answer in turns, starting with the biggest group and working down to the individual answers.
Participants then think of new categories until a someone gets an idea and steps forward as the new joker.
This game lends itself to thematic play: the categories can be "contract", "part-time job", "union", "capitalism"...
People answer with music instead of words. So, for "Paris, France" a participant might whistle or hum part of Gershwin's "American in Paris," or Piaf's "J'ai deux amours," or the "Marseillaise." The joker can also give musical categories, like "country music", or artists, like Beethoven or The Clash. Again, the object of the game is to find an answer that others will also find.
You can use music, gestures, attitudes...