Alright, so when I mix stuff I usually get a bunch of audio tracks that I need to make sense of. I have a template for this and I begin with putting everything in folders. One for Drums, one for keys, one for vocals etc. When all that has been taken care of I'm pretty much ready to begin mixing. However, I also like to keep my projects as small as possible. Today most audio software isn't too picky about stereo and mono files and Reaper especially takes good care of anything from mono to multi channel audio. There are however many advantages in keeping your mono material in mono files and stereo material in stereo files. The first one is file size, a kick drum or a lead vocal for example, are in most cases mono material. I usually or at least often get those as stereo files. If I could make them mono instead the file size would be cut in half, and that can make a lot of difference in a say 60 track mix project. The second benefit of keeping your mono files in mono is processing power. Plugins that get mono material instead of stereo material won't have to work as hard and your CPU will have to do less heavy lifting.
So what to do about this? You could always ask for mono and stereo files from the person that sent you the files. Even though that's good practice for bouncing out tracks it's a little tedious and will take up time not only from you but the one that sent you the files. You could also use Reapers right click item list and pick "take channel mode: mono" from the "item settings" menu. That is also a bit tedious though and you'll have too find out which files are mono yourself. Now to the most boss way of doing it. In reapack (www.reapack.com) there's a script called "true stereo test take". This script will compare the left and right channels of your audio and determine weather they are different or not. If they are not the script will make the item mono! So you can just select all the items in your project, run the script and then glue the items again. If you want to shrink your project folder size don't forget to clean up the project directory in the "File" menu.
That was my Reaper tip for today! If you have any questions about the script or anything else you can use my site form to send me a question!