What is the simplest instrument to play?

The simplest instrument to play is arguably the kazoo. It is a membranophone that adds a buzzing sound to the player's voice. The kazoo consists of a tube with a membrane at one end and a hole at the other. The player hums or sings into the hole, causing the membrane to vibrate and produce sound. The kazoo is easy to learn to play, requires no prior musical knowledge, and is fun for people of all ages.