This free version allows you to select game types with up to 5 notes. In the Pro version, you can select game types with all 12 notes, or any combination of notes.Based on old-style classic arcade games, "aliens" descend upon your home planet, intent on destroying your prized collection of musical instruments. It's your job to blast them out of the sky by recognizing the pitch that they are playing, and playing that pitch yourself before they reach the ground. If they reach the ground, one of your 15 musical instruments is destroyed. Once your instruments are all destroyed, it's game over! As you blast the aliens, you can move up to harder, faster levels.