What Is the Functional Diagonal Approach on Guitar?

Office HourFunctional Diagonal ApproachFDA
Written By June
Go Watch Video

What was the question?


A member named Jenya had been reading content from the VoiceLid Jazz Guitar Threads account and wanted to understand what the Functional Diagonal Approach actually means. She had not come through YouTube but through the written content there — and the question was a direct one: what is this diagonal fretboard approach, and what makes it different from standard scale-based methods? The question opens right at (00:02).


The core idea (in plain English)


The Functional Diagonal Approach (FDA) gives you a binary decision on the fretboard: for any chord in a progression, you play either the West Line or the Django Line. Which one you choose depends on the chord's function — tonic or non-tonic — not on what key you are in or what scale fits the chord. (01:35)


In the key of B-flat major, for example, G minor 7 functions as a tonic chord, so you use the West Line. E-flat major 7 functions as a non-tonic chord, so you use the Django Line. The two lines are diagonal structures that run across the fretboard. You are not following a scale from root to root — you are targeting specific chord tones along a visual path that stays consistent regardless of which chord is currently playing. (03:16)


This approach explains how self-taught jazz guitarists like Wes Montgomery, George Benson, and Russell Malone built their lines. They were not thinking in Ionian, Mixolydian, or Dorian. They were playing blues-based lines that respected chord function and voice leading — which is exactly what the FDA describes and teaches. (12:43)


Fretboard breakdown (what to play)


  • The West Line is a diagonal structure built from a minor 7 shell voicing with the root on the sixth string. From that shape, you can extend upward, building stacked thirds — the upper structure chord that sits on top is also part of the West Line. (01:35)

  • The Django Line arises when you locate the same chord with its root on the fifth string. The upper structure triad that appears above it takes a different diagonal shape across the strings. (03:16)

  • In Autumn Leaves, the first three chords (C minor 7, F7, B-flat major 7) move from Django Line to Django Line and then resolve to the West Line. The next phrase begins again on the Django Line. You are not choosing a new scale for each chord — you are simply staying on the correct line based on function. (05:03)

  • The guide tone — the third of each chord — is what you are specifically targeting as you move along each line. The melody of Autumn Leaves is built directly around that guide tone movement. (10:15)


Go Watch Video

Common mistake to avoid


Most guitarists approaching the FDA for the first time try to treat the West Line and Django Line as scales — fixed note sequences to run up and down. That is not what they are. They are diagonal frameworks on the fretboard that show you where to be, not what exact notes to play in a specific order. The note choices within that framework come from targeting the guide tone and building outward from there. If you think of them as scales, you will play them mechanically. If you think of them as structures for chord function, you will hear the harmony. (08:27)


A 10-minute practice assignment


Take Autumn Leaves. Play just the shell voicings of the first four bars — root, third, seventh — and then remove the root so you can see the inner voice movement clearly. Notice that the inside voices move by half step. Now assign West Line or Django Line to each chord based on its tonic or non-tonic function in the key. You do not need to play full lines yet. Just see where on the fretboard each diagonal structure lives for each chord change. Do this slowly for 10 minutes. The goal is to see the binary choice, not to run lines over it. (10:15)


How to join the next Office Hour (Free)


The Office Hour is open to all members of the Essential: Building Blocks course, which is free to join.


June
Next

Ditch the Scales: Voicing-Centric Improvisation and Upper Structures