In the 90s the book Behold A Pale Horse was popular among rappers and a lot of rappers were inspired by this book.

Immortal Technique - Cause of Death

... You think illuminati's just a conspiracy theory?

That's why Conservative racists are all runnin' shit

And your phone is tapped by the Federal Government

So I'm jammin' frequencies in ya brain when you speak to me

Technique will rip a rapper to pieces indecently

Pack weapons illegally, because I'm never hesitant

Sniper scoping a commission controlling the president ...

Pusha T - Doesn't Matter

“Since y’all claim I’m Illuminati, tell me why would you try me?

Kennedy, John F., or Bobby

Almost caught Reagan, but they stopped us at the lobby

And that was broad day, so how the fuck you gon’ stop me?”

Hopsin - Nocturnal Rainbows

"...The change he's making isn't good, that's just how you conceived it

It's like we all broker than ever, it's due to reasons

Dealing with self-beneficial plans and the movement he's with

Illuminati, or whatever they go by

They’re the reason real events happens, and we don’t know why”

Gamma Ray is a metal band which has created an album about the New World Order conspiracy theory called "No World Order". The first song, Introduction has the following lyrics:

“Illuminati

You've come to take control

You can take my heartbeat

But you can't break my soul

We all shall be free

Illuminati

You'll never take control

Your new world order

Will lead to none at all

We all stand before you as one

Heaven is for everyone

To be free from the dark”