A few years ago I started a test project that would allow a user to have fine grained control over a tone by drawing the frequency and volume envelopes themselves. I've since come back to the project and added a little polish. You can find the app below.
Still not convinced? Check out this sweet screenshot showing a tone with an approximately gaussian volume envelope and a chirping frequency.
Notice that the above interface is very simple: - "Play Note" does exactly as it sounds (makes a sound) - "Toggle Line" switches between volume and frequency input - The slider allows you to change the timescale of the program With that in place you can freely draw on the canvas to creat the tones of your dreams!
Now go ahead and create your own sounds! Please share anything cool you come up with!