Are you familiar with Overtone[1]? I'm no musician, but as a developer I'd think building your own musical abstractions via code would be better than any visual IDE.
Images are inherently visual, and they seem to have more irreducible complexity than music. Music has a lot of structure and repetition that seems like it could benefit from abstraction (as Chris Ford demonstrates with some Bach in this entertaining talk[1]).
On the other hand, there are vector graphics editors that let you work in terms of shapes and paths instead of pixels. Would you say you are trying to build the musical equivalent of that?
I'm aware. However the scripting is like an extra feature, not the main interface. The OP was saying that code > UI, however I disagree. It's useful, however not superior.
OP was saying that code > UI "for developpers". Something like one of Brett Victor's UI[0] integrated in GIMP would be quite nice for a dev who can draw, or a painter who can code.
[1] http://overtone.github.io/