Hold down the keys (refer to the picture below) for the note you want to play and blow in the microphone that is located in the lower right corner or if you are using an external microphone blow in that.
iPod Touch (1st generation) can’t make use of the microphone so sound will come by just pressing the keys.
(Notice that you must hold down a “correct” key combination or no sound will come out).
You change the octave by tilt up or down.
In the beginning it might be a bit hard to control your fingers so we recommend you to practice using the background music.