$2 on the App Store.
[see a cool user-made song]
In the first part of the demo, we see that when a node is hit by a pulse, it generates more pulses. Different kinds of nodes create different patterns of pulses.
Square nodes don't generate any pulses; X-nodes block pulses completely. Moving around nodes or changing their shape can radically alter a noteplex song!
You can also assign a finite "life" to nodes -- nodes that turn off or on after a certain number of pulses hit them. Your noteplex will change over time adding complexity and richness to your visual compositions.