It's not really a 'lead', pore of a gated pad.

Chose a pad sound you like then you need to automate various parameters to achieve the effect, for example the filter, phasing and amplitude. You could automate using your DAW or some synths and products have facilities to do this (such s camel phatt).

It's a pretty tired old sound though so you would need to bring something new to it or people would find it cheesy.

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https://soundcloud.com/butlerrichard

I likes that track alot

Sounds like a gated supersaw pad to my ears, maybe with a chorus effect on it but, its hard to tell with the quality of the youtube player.

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www.soundcloud.com/timestretcher