I am very far from finished (also because this is just a prototype and I'd like to completely re-implement it, using the NetBeans Palette API), but here's what it looks like so far:
If you want to see the MIDI Editor in the context of the entire IDE, click here.
Even though it is only a simple prototype, the MIDI Editor can already do a lot:
Player player = new Player();
Pattern pattern = new Pattern(MidiEditor.getText());
I've added the example tunes that come with the JFugue documentation. Below the editor, you see a short list of these. When you select any of the items in the list, the related tune is immediately played.
I don't think it should be very difficult to reimplement this user interface in such a way that notes, on buttons, can be dragged and dropped onto a music sheet implemented in a topcomponent. That's the next feature I'd like to implement. Also, code completion in the editor would be a very cool enhancement.
By the way, it took me about a day and a half to implement this user interface for MIDI and JFugue (without knowing anything about either MIDI or JFugue when I started). Anyone who knows me knows that I am definitely not a programmer. And, therefore, I think that this says a lot for the simplicity of JFugue and the productivity of NetBeans IDE.