I'm actually working full time on a new DAW that should make writing music a lot faster and easier. Current DAWs don't really understand music. Also the note input process and experimentation is extremely time consuming and the DAW never helps. Current DAW : my thing = Windows Notepad : IDE. The HN audience is definitely one of my core groups.
If you are interested, sign up here https://docs.google.com/forms/d/1-aQzVbkbGwv2BMQsvuoneOUPgyr... and I'll contact you when it's released.
I think my idea of a perfect music program is closer to vim than an IDE, but you're on the right track.
Have a look at extempore, a lispy live music/notation language and environment. Only emacs bindings, no vim, but impressive preformance nevertheless...