I have been working on a very silly Xenakis-influenced graphical cloud synthesis program. The working Alpha version is far enough along that I can release it into the wild. Improvements, like being able to save, will be forthcoming. If there is adequate interest, (ha!) I'll put this on sourceforge or something, so it's easier to get updates.
This program is so cutting edge, that you will need to download a build from today or newer from Wesleyan to run this. Grab the one called Most Recent Build if the file size looks reasonable. (around 6.2 mb or larger.)
There are two files: scribble.rtf and Cloud.sc. The best place to put Cloud.sc is ~/Library/Application\ Support/SuperCollider/Extensions/Les/ (create it if it doesn't exist) or, alternately, you can drop it in SC/SCClassLibrary.
To run: after you've put Cloud.sc in the appropriate place, start the SuperCollider application. Hit the boot button on the localhost server window. Open scribble.rtf. Select all. Hit enter (not return, they're different keys). Start drawing in the big scribble window. To change parameters, hit the draw / edit button. You need to click it when it says "edit" to go into edit mode (I'll fix this soon) and then click inside a shape. A dialog box will come up, which you can use to change parameter for that one shape only (group select is coming soon). To play, click the button that looks like [ > ].
Rain Clouds is an mp3 created with this toy . . . err, tool, I mean.
Obviously, this is open source. The cloud shapes do not need to control granular objects. Cloud's instance variable, settings, should be an instance of the Conductor class. Therefore, you can change all of their settings and what the parameters mean. Use the shapes to control filters or anything else where a high and low frequency boundary change over time! Standard software disclaimers apply.