Cryrez is a sound game -- you sing and crystals resonate.
Sing for the crystals! It's sort of a vocal warm-up, sort of a vocal pathology inducer. It's less a music game and more a sound poetry game.
You'll need a microphone, and to select the right sound source from the starting menu. From there you'll just need to make odd whooping sounds and hope.
A little more help selecting the sound. On my computer, using the rock band USB microphone and the on-board sound output, I need to click on the two places with arrows drawn near them in this picture.
Two videos of the included level:
Gameplay (game sound) -- this has a recording of what sounds the game is making (sound is slightly off sync).
Gameplay (player sound) -- this has a recording of the tones I'm making.