Before you decide to use REX or ACID files in your Pro Tools session, you need to have an understanding of what they are.
I will describe here the basic method of using them within a Pro Tools session. It is up to you to figure out how to make them work in your sessions for what you want them to do.
Edit July 15 2009: In Pro Tools 8 and above, you will need to first check your preferences to make sure they are setup properly. From the menus within the program, go to Setup -> Preferences, select the Processing tab, and make sure that “Import REX Files as Region Groups” and “Automatically Create Fades” are selected, and make sure to make the appropriate selection for “Drag and Drop from Desktop Conforms to Session Tempo” is selected (either “REX and ACID File Only” or “All Files”). Also, much of what can be done here with REX/ACID files can now be done with the elastic audio features.
- Create a stereo audio track
- Drag your REX/ACID loop from it’s current location into the stereo track you just created (DO NOT use the Pro Tools import audio function, as this will convert the file to a basic audio region). If it is a properly created and sliced REX/ACID file, the Region Group icon will appear on the region in the track in Pro Tools.If it is not a properly created REX/ACID file, no icon will appear and it is treated just as any other audio region. In those cases, you will not be able to use those files in this manner without editing and slicing them on the beats yourself.
- Once the region is in place, you should play the session to ensure that it is being time adjusted to the session tempo and crossfaded correctly. The region should match the Pro Tools session tempo, and crossfade all of the slices. (If you are not using Pro Tools 7.3 or above, there is no automatic crossfade functionality, and I would strongly recommend upgrading)
- Select the Loop Trim Tool
- With the Loop Trim Tool selected, hover over the end of the region, until the cursor changes to the loop trim cursor
- Click the end of the region with the Loop Trim Tool, and drag the cursor to the right in the timeline for as far as you want the loop to repeat.
That’s it! Those are the basics of using REX/ACID files in Pro Tools.