Here's our collection of various web music experiments built by us or other creators.
Ambient drone box is an experiment where simplex noise meets generative music.
Here's the universal Fretboard calculator that may help you build your own custom fretted string instrument with any given dimestions.
We haven't ported the fabulous MIDI Paper visualizer yet, but you may play with it standalone. The Sound Laboratory is another powerful standalone tool to explore basic sound synthesis and effect chains. Some even more old experiments are at Dev.
The Spectrum analyzer is a basic sound analysis visualization to build upon..