Watch the A Slow Blues online guitar lesson by Larry Carlton from 335 Blues
There are many ways you can change the character of a rhythm part even if you keep the exact same rhythmic pattern going chorus after chorus. Here's one method that I find works nicely over this slow blues in A.
What we're going to do is "approach" each chord with its own V minor. In an A blues, the changes are A - D - E7, right? Let's call those our "target chords." Here are the target chords and the V minor approach chords for each:
TARGET CHORD V MINOR (Vm) APPROACH
What we do is play the approach chord before its target chord. So what I'm doing in the video is playing three choruses of rhythm. The first features just the standard blues changes in A. In the second chorus I bring in the Vm approach chords, playing one before each target chord. In the third chorus, I mix it up a little with new chord voicings, but they're all still Vm approaches and target chords.
Not to throw you, but I'm also using some basic chord substitutions in here. Rather than A - D - E7, I start with A13 - D9 - E9. I can make similar substitutions with my approach chords, so instead of plain old minor chords, I often play min7's and min9's. Ultimately the changes look more like this: