Awesome interface, Awesome idea.
This is a neat little sound gadget that has massive potential. Your interface is intuitive while still providing complex sound mixing possibilities. The only reason I didn't give a 10 overall is because I think you could have used much better sound clips.
My suggestions:
- If posible, use sound clips that work together, like the different instruments in the same song.
- Try to synchronize each different sound clip, so whenever you add a new "+" symbol, the resulting sound is playing in time with any other tracks already playing.
- Expand the gadget with different "Sound Sets" users can choose from, each offering a unique set of sound clips. (e.g.: "Sounds of Nature", "Heavy Metal Mixer", "Smooth Jazz Clips")