For the audio easter eggs, they are located in Club Errera. Continue through the mission until you get the notification to go to Club Errera. It will mention Hunters blocking the jamming device. Pay attention to where the hospital is located (this is the objective where you hsve to fight through Brutes going in and Jetpack Elites going out).
Fly over to Club Errera to activate it once it has become the objective, then turn around and fly to the hospital. On the mid level of the outer area of the hospital you should see a small courtyard-like ledge with two trees. Land on this ledge and look for a green switch on the wall and activated it. Get back into your Falcon and fly back to Club Errera.
Once you head inside the inner dance floor area will now be jumping with a Brute DJ playing music and Grunts poppin’ and lockin’ on the dance floor to pop HBOrg Special. If you didn't pop Front Page News when entering Club Errera on your initial run, it should pop now (it did for me). Once you’ve witnessed the DJ Brute and dancing Grunts, go back out to your Falcon and fly up to the rooftop of Club Errera. Activate yet another green switch on the wall beneath the air conditioning vents on the left side of the rooftop. Go back to the Falcon and fly back down to re-enter the club’s dance room. You should now hear Siege of Madrigal playing.
This solution will unlock the following 3 achievements: