I think you're right that significantly improving the status quo is really hard, but I think that there is room for small improvements that seem to be overlooked.
Stuff that seems to be taken for granted, like tooltips, cursor changes for functionality, identifiable buttons/controls, could all go a long way. The difference between something like Lightroom and many of the premier synthesizers is pretty staggering. Not that they're perfectly comparable, but that's another topic.
This is a way to simultaneously interface multiple linear controls without having to point and click or even look at the screen. Some of this was inspired by Englebarts key cord in his 1968 demo and keyboard based Raskin style quasi modes as described in the Humane Interface.
Go to http://9ol.es/input.html on a desktop.
Hold down any combination of the 1, 2, 3, and 4 keys on the keyboard with one hand.
With the other hand, move the mouse either up or down.
You will see that by pressing down the key, you've selected one or more sets of the numbers, indicated by them turning bold.
Then the mouse moving will affect only the selected "controls".
This cognitively frees the user from the task switching of engaging with the interface while composing.
It also detaches the layout on the screen from the interfacing of the computer and presents a new generic paradigm of using the computer.
There's an additional demo I have that changes the background color to indicate a mode so that a bank of keys can be assigned to setting traditional modes on top of the quasi modal interface.
The objective is to have a system that can be modified quickly and simultaneously with minimal active cognition that distracts one from the artistic task.
Easy to use and easy to learn are distinct things. Usually the latter is done at the expense of the former.
In the long term, I am making this a virtual midi device that can be interfaced into any music software that accepts midi devices.