What I did so far (and turned out to be relatively similar) was creating a square wave, put unison to 2-3 and play around with detune a little and adding portamento, a little EQ and reverb. If there's a better way let me know!
But the most important aspect I can't figure out how to create is this whiny and even a bit whale-ish kind of sound (which is audible in both songs' lead melody) if you know what I mean
Obviously the portamento is an important aspect but there's definately more to creating this whiny sound, maybe a second osc, do you guys have any idea?
And If you have any idea on the second-link-lead-sound feel free to tell me Thank you!!