Many students have come to me over years with the same problem; they can play a few songs (and perhaps quite well), but they have no understanding of what they are doing and they feel like they’ve hit a brick wall. This is a very common plateau I believe many “self-taught” guitarists hit.
One of the many tools that can be used to learn the higher positions is the CAGED system. Though the application can be very useful, aspects of it can be simplified and studied in a more musical approach. Doing this might help you have a better understanding of chord voicing and harmony.
This riff-writing exercise will demonstrate how to create diatonic and borrowed chords based on a chromatic bass line while staying in key. For this example, I’m going to use the key of A minor and the harmonic minor scale as my guide for chord construction.