Harmonize a Melodic Line with Block Chords
In classic big band jazz, the horn section would often play the melody of a song harmonized in four or more parts. This technique of harmonizing a melodic line with full, dense chord voicings is sometimes referred to as using block chords. Pianists like Lennie Tristano, Oscar Peterson, and George Shearing all used block chord techniques in their solos, and they were very proficient at approximating the sound of a full horn section. Montgomery, being influenced by big bands and these pianists, played block chords throughout his improvised solos, often creating an incredibly exciting finish to a three-tiered solo that started with single-note lines and worked through octaves and finally block chords.
Example 6 shows a simple Gm line with the notes on the high E string, followed by block chords harmonizing each note in the line. In this case, the block chords are simply Gm7 chord inversions. But you can also use other strategies for harmonizing, particularly for scales. Example 7 harmonizes a Gm line with a pair of chords: Gm7 (G Bb D F) and Am7 (A C E G). This works beautifully because if you were to put the chord tones of those two together, you’d have a G Dorian scale (G A Bb C D E F G).
Excerpted from Fingerstyle Jazz Guitar Essentials: Orchestral Improvisation