The Alternating Bass
In previous lessons, we played country backup parts by hitting a bass note on the first beat and following up with three downstroke strums (or two downstroke strums for a waltz). Now we’re going to add in another bass note, on the third beat, replacing one of the strums and giving us the classic country and bluegrass sound of an alternating bass.
Let’s start with a familiar chord, D. For now, our general rule is: for the second bass note of the pattern, go up to the next highest string (meaning the string with the next highest pitch, not the one higher off the floor). So for a D chord, we’ll play the second fret, third string, on beat 3, as in Example 1. Everything is still done with all downstrokes (toward the floor).
On an A chord, if we follow the general rule of going up to the next highest string for the bass note, we’ll play an E note, or the second fret on the fourth string, on beat 3. It will sound like Example 2. You’re now playing a bass note on every other beat, and following every bass note with a downward strum on the top strings.
Excerpted from The Acoustic Guitar Method