The double tracking of vocal and guitar parts is one of those time honored techniques of “modern” recording. Over the years many variations on the basic technique have been used. None sound quite the same, but many of them stand on their own as interesting sounding production elements. One of the more common variations is to use some type of delay and/or pitch processing to synthesize the effect. There are a lot of ways to accomplish this, but if you take a mono guitar or vocal track and run it through the SuperTap Delay plug-in from Waves with the original panned 45 degrees to the left and a very short delay panned 45 degrees to the right, you get a nice “double” effect. You might add a little extra high-end boost on the delayed signal to help give it its own character. The non-elegant version of doing this is to clone the track (and all its effects) and slide the clone in time. Using SuperTap Delay is much faster, easier and the results will better.