BlokDust

BlokDust is a web-based music making app. By joining blocks together, you can build synthesizers, put effects on your voice, remix & manipulate samples and arrange self-playing musical environments.

You can share what you make and if you want, you can expand on other people's creations. You can also contribute by tagging your tracks in SoundCloud with #blokdust so that your music is available for people to play with in the app.