Enhancing the Alternating Bass with Passing Tones
The chords of an alternating bass pattern can be connected by way of passing tones that form steps and runs in the bass line. Passing tones are notes that don’t belong to the chord being played but can be used to add emphasis to chord changes and to create a more contoured bass line. A step is usually one or two notes, and a run is typically longer and often more elaborate. Both are usually accented. In the first measure of Example 1, the accented bass notes on beats one, three, and four step from G to B by way of the passing tone A. In measure 3 the bass alternates down to the passing tone E on beat three and then steps up to the F# on beat four, resulting again in accents on beats one, three, and four. In measure 4, the bass line plays a four-note run by way of the passing tones A and Bb, respectively on beats two and three, resulting in accents on all four notes.
Excerpted from The Alex de Grassi Fingerstyle Guitar Method