Find a way back to the Composer | Midnight Halo 4 Guide

When you defended the point, take Cortana from console and move through to the next portal on the higher floor. Go to the end of a ramp, where you'll be transported to the other side.

There are weapon stands and modules in front of the door. But I recommend to keep an Autosentry. Go through door and use a panel shown on the screen. You'll get two targets. Firstly , go right. Use a jumper at the end of platform to get on the other side.