Lead sound question (audio examples inside)

Hi,

Can anyone here please explain how to create a similar lead sound like these (there all almost the same):
http://youtu.be/iUKCUOnANso (@0:44)

http://youtu.be/UvJsvAGBJ3I (@0:15)

http://youtu.be/MwIChcZMVV0 (@0:40)

http://youtu.be/jHsjaa2zbR8 (@0:27)

Thank you!

Zitat von rensvanlaar

it are square waves with a sine LFO on it i think, it also has portamento on it.

Could you try to replicate it? I prefer this sound:
http://youtu.be/iUKCUOnANso (@0:44)