Tonematrix is a site that generates sinewaves in a pattern that you determine. If that sounds complex, then go ahead and click here, then draw something on the grid. It’s far easier to understand if you just give it a try. Far easier than understanding the developer, who says:
“The sound generation is basically a polyphone synthesizer with a simple delay with a variing read-offset to make the tones vibrating in the end.”
Despite the fact that the first thing everyone will do is draw a penis, there’s actually quite a sophisticated synth running in the background. It’s possible to make loops that sound pretty awesome. What would be even more awesome is if you could adjust the BPM on the fly. Or use it to play Battleships with a friend. Either would do.