Take Ex. 1, for instance, which features three layered lines. As you fingerpick this moody two-bar phrase, notice how you’re moving up and down the sixth and third strings, using major tenths (found in Fmaj7 and G6) and minor tenths (Am and Bm add4). The shifting major and minor tenths each represent a burst of parallel motion. But wait: Ringing above is the open first string, which establishes oblique motion in relation to the moving harmony below.
Ex. 2 presents another mixed bag. The upper melody rises and falls over a descending and ascending bass line, resulting in a harmonically rich, harp-like progression that mixes oblique and contrary motion. Work through this slowly, first practicing each chordal move by itself, and then linking the two-beat segments to their neighbors.
Learning to identify parallel, oblique, and contrary motion—and exploring ways to blend these sounds—will help you play better and give you insights into composing and arranging guitar music.