This is the kind of question that we all ask ourselves, explicitly or implicitly, but I’ve personally found that is a challenge to work through and a task that is easily derailed. I would suggest that the question be reframed. Instead of “what instruments are playable,” I would ask yourself “how would I like to interact with an instrument.” Upthread you clarified that you are specifically “not really interested in diff ‘sounds’ but control of them,” so I think this is actually what you are asking, but by reframing it explicitly this way, the focus is where it belongs — with the player, not the instrument.
The advantage of a modular synthesizer is that it’s an open-ended system that you design and which has an infinite ability to be reconfigured. The disadvantage of a modular synthesizer is that it’s an open-ended system that you design and which has an infinite ability to be reconfigured. In contrast, the advantage of the (original) Minimoog is that it is a self-contained system that has well-defined limits, and the disadvantage of the Minimoog is that it is a self-contained system that has well-defined limits.
To focus your question further you could provide more details about what you need out of your instrument and what trade-offs you are willing to make. The expressiveness of an instrument is 100% about the performer, and that performer’s ability is dependent on spending a significant amount of time honing their skill. I would argue, with only slight exaggeration, that one could devote one’s entire life to the Korg Monotron. It looks like a toy, but is it really that much less expressive than a flute? Of course that doesn’t mean you could devote your life to it or that it satisfies any or your personal criteria. What is it about an instrument that would inspire you to come back hour after hour, day after day?
