Soundrop is a sound toy application for iPad, iPhone & iPod Touch which allows you to create sounds by drawing lines on the screen and have ball bouncing off them. Each time the ball touches the line, a sound is generated. Depending on the location of the line on the screen, the tone of the sound is set. You can move the ball emitter, changing the nature of the composition. You can modify the location of lines by dragging points that define them alternatively double tap on any line will clear it. Wonderfully simple and a lot of fun to play with. Check it out..it's free.