I’m inclined to believe it’s the OP-1.
It invites you to play it, find a hook, work within the bounds of the given instrument type you’ve selected, and play that hook into the tape recorder.
The limitations point you to the song writing. No velocity, no “standard synth features”. Just a couple octaves on some clacky little keys.
Melodies are ideal in this context.
I had one years ago. Amazing how big the sounds can get on it. I did Fanfare for the Common man on it. Trying to emulate the Yamaha of ELP at the stadium. It was dang close.
On the OP-1, eh? You have a recording of that?
I’m just curious what that sounded like, is all.
Sadly not. I got the opening bit and then tried to do the rest but it fell apart as a project with Greg Lakes guitar/Keith Palmers drums and the timing. In hindsight you should keep everything. I didnt have to do much but there is one factory patch i remember which was very close already. Should have kept it as i had a lot of fun with it.
any Mono synth, Legato mode with Vibrato, glide and pitch bend
What have you got currently?
Honestly, when you think about it, its a daft question. If you cant write a good melody, it doesnt matter what synth you have.
If its about the keyboard, then use that as the decider. Some are shitty (MS20) some are very nice (waldorf blofeld keys)
A midi keyboard plugged in to what ever, will do the job too.
Or just get a Pulsar 23. Best melodic synth in 2021…
Melodies are often overlooked. With Synths people tend to focus on pads or textures. Now some synths are designed for melodies. The new Korg 700fs reissue springs to mind. (Surprised this hasnt been mentioned)Where many great tunes were bashed on it. OMD used a cheap Casio for their early stuff with melodies. For me it not a problem writing melodies so it is about the synth. I was as initially said trying to avoid the any synth will do reply. Some of the replies have been very useful. True a melody can sound like anything you want. But some melodies sound great sonically. Just as Pads and textures do.
Do they?
Maybe get a miniKorg 700fs?
Or a Moog whatever?
Or a Pittsburgh SV1
Or an ARP 2600
Anything with a strong voice.
I think you just mean lead sounds? You are talking about sounds you like here.
Melodies are melodies, they have nothing to do with sound or synth. You can whistle good melodies, and they stay good.
Confusing 
Yes. Lead sounds. Sorry if this got lost in semantics. Melodies are tablature just notes written down. Ive updated the title.
Anything with a good scale system, if you’re not into music theory, harmonics or similar. Properly and cleverly implemented scales will bring out the song writer in you, and while you might eventually struggle to find variations in your compositions, who cares? Kraftwerk did almost all their work in one kind of scale and Daft Punk followed the same scale and they did all right for themselves.
In that vein, the Novation Circuit OG or Tracks do this extremely well, and any grid controller that does scale in that fashion. Deluge, for example, does not do this very well in comparison, so just because it’s grid doesn’t mean it’s great for this purpose. Elektron has some catching up to do here, as well.
It would seem that most of my non-keyboard mates enjoy grid instruments with scales more than keyboard instruments, so I’d go for something from Novation.
A good scale system. Is this saying the more keys the better? Or scales built in?
Scales built in.
Circuit has the equivalent of two octaves, I believe, which you can shift up or down of course, transposing it. But if you’re not a keyboard player, a big keyboard doesn’t add all that much to the composing experience compared to just something that helps you get your ideas across, which a scale system does much better. Through the ages, many great songs stay on scale and sometimes also even just within one octave - twinkle twinkle little star, we are the robots, oxygene, without you (the Avicii track), and so on.
Anyone is capable of writing a great song. If you’re not schooled or trained in an instrument or in music theory, an instrument that lets you play within a given scale will bring out the songs within you, eventually.
This makes thread makes way more sense now. I’ll stand by my previous list.
also the Korg monologue is another very good budget option in my opinion.
I’ve heard someone call it very guitar like, which somehow is true…seams like the lead guitar of the synth world to me.
I would say the Minikorg 700FS is the best sounding for leads in my experience. Also the controls are very intuitive and well suited for leads. The palette of sounds is insanely wide and characterful.
Interesting. That wide gamut of lead sounds i need to listen to more. 
