It's super easy to play without any special knowledge, just by singing into ir. I got three different and each has different sound, that's cool. My favorite one from them is Flight KZP Elise Ecklund. But this one is good too. In general I feel that the metallic ones sound better. But each kazzoo is suitable for different tunes I guess.
It's easy, cheap, small, therefore one of the best instruments for me.