Wasn’t the Model 15 like $10,000?
If software is an option, this is pretty good:
Can be done on phones, laptops, whatever. Browser based.
Could also be a nice addition to any hardware choice.
I think this is a great shout since it makes a wide range of sounds and the layout is pretty clear. Fx built in too. In budget and portable. Also medium size keys for smaller hands.
Kobol. It’s cheap, it sounds great, it’s knob per function, the signal path is silkscreened on the front and it’s got all the patch points you need for when your teaching gets a bit more advanced
I’m not particularly happy about the idea of putting B-ger product in front of impressionable young minds, but one can get three Kobols for the price of a Bullfrog, and I have to be mindful of the dire state of educational funding in most jurisdictions. Kobol is at least a revival of an old obscure and rare device. It does seem like a good possibility.
I meant Behringer Model 15! I’ll change that in my other post
Agreed. With hydrasynth you can see the entire path. And it has a lot depth. People can learn a lot for that synth.
A Hydrasynth is going to be a lot for an eight-year-old to deal with!
I went through this with my kid. I wanted:
- classic simple subtractive knob-per-function layout (lots of these around)
- polyphony because if you’re just learning keyboard you should be able to play chords, etc
The only real option is the Minilogue. Not XD imo because the added complexity of the digital osc isn’t necessary (plus the added cost).
I really think that it’s very easy to understand and you can go very deep with it. It’s no the typical one filter one osc analogy monosynth. You can begin just with simple with just one oscillator, filter and amp 
Another easy is the Crea8 East beast. Aroeggiator, sequencer, very easy to use, with keyboard buttons… And hidden options. And you can use cables to patch. I like how it sounds and is a very simple monosynth.
I think it will depend on the ability of the child to deal with abstraction. Some adults can’t manage it. There is metaphorical power in patching with physical cables.
My son when he was 11, figured out my Korg Monologue (with a few questions) in a very short time, and still grabs it periodically to noodle around. Simple mono synth; sounds good; basic sequencer; no menus to dive through (knob per function); left to right layout pretty much.
I still grab it to experiment with patch creation and to refresh my brain. It’s basically a subtractive synth tutorial in a box.
You can get them used for $200 or so. You can get used Minilogues for around $400 and have a simple starter and an ‘advanced’ for kids that ‘get it’ for right at your budget. Minilogue is a bit much for an 8-year old, maybe, but they pick things up quick so…
I think it has some big advantages over a monologue for a kid. The two oscillators are identical, you get two full adsrs, the layout is better like the location of the lfo. The big cutoff knob. The whole design is just a little clearer and more classic imo. You get noise in the mixer, you get delay which is a great first effect to learn. Plus I think it’s only natural for kids to want to play more than one key at a time.
Also the waveform display on both of them is a great learning tool.
Yeah
It’s certainly more fun down the stretch.
My son, to add to your comment, did move on pretty quickly, so maybe it’s me that’s slow, lol
He wouldn’t touch the minfreak first, but loves it now
I vote for GM/model 15 as well
I like both suggestions of Korg Monologue or Behringer MS-1. I think I would lean toward the Monologue.
To make future synth-wizards “understand” what they are doing I would recommend to teach on modular gear and not restricted to east or west-coast concepts … 
IMO it’s a good start to see and manually connect “sound generators”, “sound modifiers”, “modulation sources”, and “typical utilities” with patch-cables. This also invites for experimentation, because there is more than the “standard subtractive synthesis”, which we find almost in every synth on offer in a shop.
I would build a basic system with two classic VCOs, two different VCFs, two VCAs, modules for wave-shaping and wave-folding, two LFOs, two ADSR and two AR envelopes, a mixing section for modulation signals, and a mixing section for audio. With some utilities like mults, ring-mod, etc. this would allow many different ideas to sprout. A keyboard and a sequencer would also be useful 
I’d probably go with the Roland JU-06A or SH-01A if I was doing this myself.
They both have relatively simple architectures, clear signal paths and basic sequencers/arpeggiators.
I also think having a full ADSR envelope would be useful, as this is perhaps one of the more difficult concepts to grasp for complete beginners. Some of the suggestions above have more simple envelopes.
The synths these boutiques are based on have also be so widely used that you could easily find reference tracks to try to emulate – quite a good way to learn.
Oh yeah, and they sound cool. In fact, I’m tempted to pick one of these up myself now…
Your description is pretty close to the new Music Thing Modular Workshop System. Unfortunately, it’s only sold as a DIY kit currently, for £400, in small batches that one has to get on a waiting list for. I hope it takes off enough for a fully built option to become feasible.