Add Scratch Rhythms to Your Acoustic Rock Strum Patterns
A great way to add a percussive pop to your rhythm patterns is to play scratch rhythms on beats two and four of each measure, simulating the sound of a backbeat snare drum. Example 4a shows how you might do this for a thick C chord. Make sure to damp all the strings on beats two and four by lifting your fretting-hand fingers off the strings just enough so that they donâ€™t ring out as you strum through. You can add extra pop by slapping the underside of your picking hand against the strings at the moment your pick connects. You can use this backbeat scratch rhythm on a huge variety of grooves, like the slow and funky pattern shown in Example 4b. Keep fretting each chord while strumming through the prescribed pattern. For the scratch strums, damp the strings with your fretting hand while you simultaneously slap them with your picking hand, just as we did for Example 4a. Youâ€™ll find that you may naturally damp a few strums on either side of these percussive strums, which is absolutely fine; just donâ€™t accent these strums as much as the damped ones, and youâ€™ll achieve the desired effect.
Excerpted from Acoustic Rock Essentials - Ten Great Rock Strumming Patterns