I already know how to create the spacing using the gradient tool. However the center image seems integrated with the spacing and not just sitting in the background.
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Looks like to me as if it's just sitting in the background. – Hanna May 4 '15 at 17:07
There's no gradient anywhere in that image.
It is merely a line pattern. You can achieve this by drawing 3 lines of varying thickness.
Select all 3 and choose Object > Blend > Make
You may need to then choose Object > Blend > Blend Options
to adjust the blend.
I think you'd have better luck with the Blend tool.
It also appears as if the center image has light lines of a constant width and spacing that match up with the gradient lines.