I wrote a python / Tkinter framework for a program which lets you create an arbitary number of canvases and draw on them. Then you can use one canvas for the notes and other canvas for volume.
The frame work can load plugins to process the drawing on the canvases and create music. I write one plugin which is extremely basic but functional. However it did produce music.
You can download it on sourceforge. search for musex or try http://www.sourceforge.net/projects/musex/
If anyone is interested in participating please send me a mail on sreekant UNDERSCORE kodela at yahoo dot com.