Honestly on a budget your best bet is to get a midi controller and hook it up to your computer as a soft synth. You'll be able to do a lot more even though it might take a bit of setup. It's hard to get a good hardware synth at such a low price but you can get a relatively good controller -- some even come with Ableton Lite.

If you want a keyboard, you can pick up an old 90s rompler for around that price. Love the keybed and build quality on my alesis qs6, but I just use it as a midi controller.

If you just want knobs and sliders, look at something like a used notation launch control xl.

If you want a full midi controller with keys, knobs, sliders, pads, maybe mpk mini? Nothing modern will have nice keys in that price range, though.

Plug in to your phone/iPad/laptop, download synth one or surge xl, spend some time mapping and away you go.

$100 is not a reasonable price point for good hardware that actually makes its own sounds, but who needs it when you have a super computer in your pocket.

I asked HN a related question.

https://news.ycombinator.com/item?id=27822489

I started with SynthOne on my iPhone.

Recently bought an Arturia MiniLab Mk II and am running Ableton live-lite it was bundled with on my laptops. <$100.

More recently I bought a used Mbox II audio interface. An eBay bargain.

Still more recently a Moog Werkstatt, Adorama had/has them for $149 because they’re closeout. And because it is a fn Moog.

And of course more cables came in today’s mail because…well because it is probably a hobby…if it isn’t a hobby it will do until a hobby shows up.

The Korg Volcas are all great fun. I'd probably go for a Volca Modular. Keys is fun, but can get boring pretty quick.

https://www.korg-volca.com

You probably won't get something worthwhile for that money, alas. If you can get a secondhand behringer recreation of a classic synth at the right money, you might be close.

I've taught music technology for over 20 years, and getting a simple subtractive synth and playing with it is the best way to learn this kind of thing. The temptation is always to get something vast and massively complex (as the presets will sound amazing), but in terms of learning how to actually program a synth, a basic one is way better. Something like the Roland SH-101 (which behringer have made a copy of) will let you understand all the elements of it that you can then translate to the complex structures of larger synths.

I find cherry audio's voltage modular a great learning tool, if you take the right (basics first) approach - as it can get very complex very quickly otherwise!

The Korg Minilogue is a really good beginner synth. It has a what you see is what you get interface, and even has an an oscilliscope which relly helps starting out. Here's a video plugging this as a great beginner's synth: https://www.youtube.com/watch?v=EE7EvKYTs4I

if you look at the recently sold on reverb, you see you can get one for ~$300 or ~$350. https://reverb.com/marketplace?query=Korg%20Minilogue&show_o...

I know you said hardware, but you also said $100. Some soft synths are worth the money, like the Korg DS-10 which can run on Nintendo DS or iOS. Check out what Anthony Seeha does with them. EG: https://youtu.be/TXTyMxM5vuY

You could also look at the cheaper Arturia synth. I really like how they sound (though AFAIK a lot of people don't - maybe take a listen to some Demos on YouTube) and find them decently intuitive for a beginner. The microbrute for example comes with a small patchbay (be careful of the modular rabbit hole though). A cursory search suggests prices between 150 and 200€ (sorry, to lazy to do conversion since I'm on Mobile). I only played with the Behringer clones a little at a friend's place. They sound totally fine, I think Arturia's build quality is way better, though. They have the benefit of being clones of popular (some may say famous) synth like the Moog Model D or the Roland 303, so they have a familiar sound.

$100 isn't going to get you much, unfortunately. Someone else has already suggested volcas, and they're probably your best bet for that price point - the only other things you might check out are the Teenage Engineering Pocket Operators, or one of the cheaper behringer things like Crave. That said, another direction you could head is to pick up a midi keyboard, and start playing with soft-synths to get a feel for the kinds of things you want to do. If you make sure to get one with midi output (not just USB midi) it'll stay useful when you eventually buy other gear.

PO-28 would be my go to. Its pretty limited in what it can do (though for the money that makes sense), but what it does it does fantastically, better than a lot of hard or soft synths I've seen for 10x that (imo, the pocket operator keypad is much more intuative than a standard keyboard).

Soft synths will of course be more affordable, you can get renoise for less than your budget which is a whole DAW. But I do recognise the appeal of hardware, no matter how many soft synths I buy it can't fill that hole for me either lol

check out the korg volca line. The volca fm 2 is about to be my first hardware synth. It’s $170 new, so you can probably find something close to your budget used.

I'd suggest to get a really great hardware synth to learn on - if you don't like it, the secondary market is usually active enough to sell it at minimal loss, and if you do like it, you immediately have a really nice instrument.

If you just want to learn monophonic synthesis with an amazing sounding synth, geta Moog Grandmother for around 1k. You can buy used and sell used, too.

Behringer typically has good value for the money. They have a couple of mini synths (e.g. behringer model D soul) which is exactly $100. The behringer neutron is around $300, so you may find it around $150 used, and it's incredible value for that money.

Korg nts-1. Same audio processing of a minilogue in a raw pcb factor. you might need an external midi controller to fully unleash it's power but those are cheap, used.

Behringer TD-3-RD Analog Bass Line Synthesizer

Model 15 Modular Synthesizer App (not hardware but close to the experience and sounds great)

Related question: Any synths/MIDI controllers that show musical scales? Maybe with LEDs or something?

I was dabbling in LMMS some time ago and it has an option to show scales but it's slow to enter and experiment with notes with the mouse.

No, I can't be bothered to learn piano scales. I expended my mental capacity for it on guitar already.