For instance, look at the simple C major melody in Ex. 1. This benign little theme works well over the II-V-I chord changes Dm7-G7-C6 and, because all that’s given is a melody and a set of chord symbols, it looks a lot like something you’d find in a fake book or on a lead sheet. As a jazz guitarist, you don’t have to stick to the written changes. You have the right to make this passage as tonal or dissonant sounding as you choose, and there are countless harmonizing approaches you can take.
For a slightly modern edge, try stacking fourths beneath each melody note, staying diatonic to the key signature of C [Ex. 2]. First, play only the notes in the upper voice (the up-stemmed clusters) to gain a feel for the harmonic pattern, then add the bass notes. Notice that although the upper voice is harmonically nebulous, these bass notes direct the ear towards a logical resolution to C. Along the same lines, Ex.3 offers another diatonic, intervallic approach to this melody that is worth exploring. This time we’re stacking a second and third beneath each melody note. As with the previous example, first play the top three notes alone, then add the bass notes. (Feel free to omit a given bass note to make a fingering more comfortable—music should, after all, be fun, not painful!)
To keep the harmony refreshing, I threw in some fun harmonic devices in Ex.4’s interpretation of our melody, including an extra “II-V” change (Ebm9-Ab7) in bar 1 a half-step above our original Dm7 (the real IIm7 in C) that momentarily takes us out of the home key. Ex.5 adds an inner melody line within the chord changes (the trick here is to emphasize the top melody more than the counter-melody, creating the effect of two instruments playing simultaneously), while Ex.6 illustrates how a melody note can be harmonized with virtually any dominant-7th chord by moving it up or down the neck in one direction—provided you resolve smoothly. And, last but not least, Ex.7 is a four-measure phrase that can be looped so you get the feel of “walking the bass” while playing chords.