This document provides instructions for mixing two songs together in Garageband by overlapping them. It involves finding two songs with similar BPMs, opening them in a new Garageband project set to the correct BPM, dragging each song into the project, listening to find the right place to overlap them, roughly placing the tracks in that spot, then precisely lining up the beats by zooming in. The example given is overlapping the songs "You Belong With Me" and "Boom Boom Pow", which both have a BPM of 130.