This game is a variation of Wink Murder.
The players sit in a circle, and a detective is selected. The detective leaves the room or playing area so they cannot see the next proceedings. Then a rhythm master is selected and the leader of the activity calls out, “when the Rhythm Master is ready, they can start the rhythm.” The Rhythm Master then starts a rhythm that everyone else mimics. For example, the rhythm master might start clapping their hands to a rhythm, and everyone must do the same. The detective is then called back to the circle and must figure out who is the Rhythm Master. The Rhythm Master can change the rhythm at any time and everyone else, once they notice the rhythm change, must also change their rhythm. The detective has three guesses.
When the game ends (with either the detective guessing correctly, or running out of guesses), the Rhythm Master becomes the new detective, and a new rhythm master is selected.