Good to see you here.

If you want to learn about a specific small device like a Theremin, there are solderless kits, some of them better for teaching than others, also some intended for quite a bit of experimentation in addition to assembling a single specific reference circuit.

IOW electronic components can sometimes be treated like Lego and judiciously re-arranged to create somewhat different projects than the one primary thing that a kit is documented to accomplish with the parts intentionally supplied for that purpose.

Plus if you really want to get creative or build more complex circuits, you can purchase all kinds of additional components individually, and add them to your collection.

You may or may not want to learn more about other types of electronic construction.

As to "where" you're going to do this, a lot can be accomplished with a solderless kit on a small worktable located many different places in a home.

But if you are ready to do more than learn or demonstrate, and want to construct an assembly which is more solid physically as well as connection-wise you really need to be able to solder, and it really is worth it to develop very strong skills for this. This can also be accomplished without the need to learn any more theoretical electronics or do any more equations than you were doing before (if any). Soldering milestones can actually be more rewarding than mathematical milestones a lot of the time too, and it's up to you what kind of a balance you want to strive for.

You can then treat the components with even more versatility than Lego since you can add things to the mix that do not naturally fit into the breadboard of a solderless layout. A worthwhile objective is to practice enough so you can almost always solder components together for experimentation without a PCB faster than you could any solderless way, so it can take some practice. There can be a great deal of confidence when you know you can just "throw together" a "quick & dirty" trial circuit with only a soldering iron, compared to a meticulous little session with a breadboard.

Regardless of experimentation, you're going to want to very carefully solder components together for something you consider a "final assembly", you don't just "throw together" one of those. Especially if you want to move the project away from the bench, or if it's musical, travel to rehearsal or performances, you need it to be tough enough to be portable, with a decent enclosure.

So soldering can be the more valuable learning experience than any one project, and require more time & effort by far to get right. The tools and familiarity with them are just as important to learn things that you never knew or expected, no different than the components themselves. So you can really make the most of it all.

For soldering don't even think about any room in the home. Whether you already have a project bench available or not you're going to need very good ventilation and put it there. You need an airflow that constantly removes smoke from the room (like a window fan facing outward) for one thing. But you don't really want a small fan on your bench making a noticeable breeze across your hot work, a fan (or "smoke-eating" filter) needs to be pointed away from your work and also be exhausting in the direction of your macro (window fan) toxin remover.

It's best if the room can have doors & windows completely shut except for the major exhaust fan, but if it's too tight and there is not enough fresh air getting in at the opposite end of the room from the window fan, you might need to crack a door or window at the opposite end of the room from the exhaust fan, so it can allow for the airflow the exhaust is capable of. Ideally somebody should be able to smoke a cigar in that room and nobody will smell it in the rest of the building, plus the smoke will clear out in less than 5 or 10 minutes at the most.

That's a lot to ask but far less limits on what can be accomplished, and there's more.

There's a difference between a project bench, an experimental bench, a service bench, and a repair bench.

I like to collect 'em all, but I've rarely had all 4 existing at the same time on separate benches.

If the tools, components, and supplies for any one function are all there you can easily get by with a single physical bench, even one more often used for something different like woodworking.

Every time you approach the bench (your honor) think about what you are going to do, whether or not you need to clear away any "woodworking" gear, then set it up for the intended task(s) and get to it. Ideally you can leave it set up until completion or when a very sensible stopping-point can be reached.

A service bench is not like the other 3 since this is more like maintenance where the patient is actually alive when they come in the door ;)

Something like upgrading a speaker on a unit that's always been working fine, just so you can have a better speaker, does not require a very versatile bench, plus almost no "trouble-shooting" abilities will be needed, nor that type of support tools.

Building a "kit" from components is like following a blueprint, and experimenting can be more like building Frankenstein's monster, but either way you're going to have to bring something different to life that was not living or not even existing beforehand.

With repair you've got to bring something back to life that at least was known to be living at one time :\

For anything that fails to come to life, or in questionable health, welcome to Troubleshooting 101.

Put that on steroids and you've got a fifth type of bench, the restoration bench. For that you're going to need more tools and hard-to-find parts than all others combined, and it's going to need to be capable of sitting there undisturbed for potentially long calendar periods when unforeseen show-stoppers are encountered. It can take a lot to raise something from the dead but even more effort to have it come out so people think it's like new after all these decades. Almost the complete opposite of Frankenstein, but takes even more of the same type skills.

So you've got undisturbed space to some extent or another, ventilation (if necessary), and the objective of bringing something to life like it wasn't before.

That could get you started, you could stay as simple as plugging Lego together, or go as far as advanced equations and/or creations performing in ways never before seen.

Setting up a decent electronics bench will take more time than actually doing one kit project, and it's worth it. In less than a month you can probably get a basic soldering bench together, in another month get good enough at soldering to avoid solderless approaches for your "musical" or audio pursuits. Then a soldered kit on the proper bench will take no more time than a breadboard assembly on a kitchen table in one night.

If you are dedicated enough to allow 12 to 24 months to get "started" you're going to potentially be able to accomplish 12x as much as the first two months like this. IOW your facility can end up over 10x as capable at the same time you should be able to build over 10x as many different projects, whether they are all Theremins or not and whether they are all identical or not. (There's also a "production" bench).

Good luck hitting the high notes on your first Theremin.

And everything else you will be capable of.