Disclaimer: I make electronic musical instruments and audio gear, some of which you may have right in front of you right now, and have a strong opinion on the subject based on decades of interacting with engineers, designers, and most importantly of all: end users.
>Casio made such a confusing mess of things with the always-on exciters, the exciter conduits and the wave shapers whose frequencies can be edited in the UI but not in the engine. It is almost a case study in what goes wrong when you lie to the user about what goes on inside the machine. Lying is a harsh word to use but when "disable" does not mean disable then I don't know what else to call that.
Other manufacturers such as Yamaha are guilty of the same kind of interface obfuscation - they have a wonderful engine, but a terrible user interface, and their development teams never get the budget they need to make the user interface problem as viable as it needs to be. You can see this in many of their products - one of the most infamous being the FS1R, which has unaccessible yet amazing features if you can pry under the hood and play with them.
Too often, the UI is bolted on at the end of the project and not considered important - or, indeed, used to cover up failings of the underlying engine architecture. Another fantastic example was the Hartmann Neuron, which was an extraordinarily powerful synthesizer engine with an interface designed by one of the industry's worst violators of user intelligence, simply to 'cover up' how the algorithm worked - because, in the designers words, "musicians don't care how it works, they just want to play". This is why the machines don't sell, people: you insult the user intelligence when you just throw knobs and menus at the problem and call it a day.
And this statement is used throughout the industry to justify half-assed, lame attempts at UI. Most of the synthesizers on the market today have UI's which are very little more than a washing machine interface, applied to sound.
A big part of the problem is that the UI is considered a section of the entire BOM where savings can be made - a cheap LCD interface instead of an OLED, "should suffice, since musicians don't care about how things are generated, they just want to play".
There are companies out there that recognize this issue with the market, such as 1010music and others. However, it is still a major problem - too often, menu diving is considered the "only way" to represent all of the parameters, without doing something truly innovative, such as actually investing in a ground-breaking interface paradigm. And, those that attempt such paradigm leaps, are too often managed into the ground by managers, whose lives as failed rock stars precludes any sensibilities that would allow them to shave margins sufficient to the task of boosting the parts budget.
It is a long-term problem. The VZ1, from 1988, is but one example of many, many products in this market segment with absolutely dreadful user interfaces. The market is ripe for a truly innovative design team to come along and fix it - just as long as they stay away from the mind-melting idiocy of the management class which currently rules the musical instrument industry.