Import into Pro Tools the two songs with which you want to create a mashup .
Select "Edit."
Choose the "Selector" tool at the top of the Edit window. This tool is illustrated by a shaded waveform.
Drag the section of the second song that you want to blend into the first song over the section of the first song where you want the mashup to begin.
Click and highlight with the selector tool the area around where these sections meet. Choosing a large section around this area will create a long crossfade allowing one song to slowly fade into the other. Choosing a small section around this area will create a short crossfade, allowing one song to quickly fade into the other.
Click "Edit."
Select "Fades."
Choose "Create Fade" and a crossfade will appear, creating a mashup between the two songs.
Import the two songs into Pro Tools.
Select "Edit."
Choose the "Smart Tool" at the top of the Edit Window. To choose the Smart Tool, click the bar directly above the Trim, Selector and Grabber tools. After clicking this bar, all of these tools will highlight and turn blue. This will allow you to use all of these tools at once, depending on where you place your mouse inside of Pro Tools.
Drag the section of the second song that you want to blend into the first song over the section of the first song where you want the mashup to begin.
Place your cursor at the bottom of the waveform where these two songs meet. When placed correctly, the mouse cursor will turn into a small gray box. This is the crossfade tool.
Click with the crossfade tool and drag your mouse away from this edit point. The farther you drag this tool away from this point, the longer the crossfade will be. The shorter you drag this tool away from this point, the shorter the crossfade will be.
Release the mouse when happy with the length of your crossfade and it will be written onto the tracks, creating a mashup between the two songs.