The diagonal lines show what happens rhythmically on each beat: whether there are hits on the beat, the ‘and’, neither, or both. There is no code for divisions smaller than eighths, or for how long a note is sustained. The background colours show the harmony. The pitch of the melody is not represented.
I have used fairly generic rhythm-changes chords – Bbmaj7, G7, C-7, F7… F-7, Bb7, Ebmaj7, Ab7 etc. Over the years, many tunes have been written over rhythm changes, and composers, arrangers and performers have developed many variants of the progression. Even for Oleo, not all charts agree.
There is nothing deep about the colour scheme. Cycle-of-fourths movement, e.g. G-C-F-Bb-Eb-Ab, is represented by a shift from warmer to cooler colours, or from the red end of the spectrum towards the violet end. I have picked different shades for two F chords (dominant and minor seventh) and likewise for two Bb chords (major seventh and dominant). If these associations don’t work for you, you could easily swap in other colours using the area-fill function in an image-editing program.
What, if anything, does the graphic tell us? It certainly shows the contrast between the tune’s simple, repetitive chord changes, and its complex, unpredictable rhythms. Of these 32 beats of music, fully half have a hit on the ‘and’ and nothing on the beat. That’s a high level of syncopation.
You may also notice that within this ‘A’ section of an AABA form, there is an internal AABA pattern in the chord changes. (Another well known tune with a nested AABA form is So What.)
Displaying the form of a tune in a rectangular grid is not a new idea. The basic idea is obvious. It’s really all about how you do it. One approach is associated with the British musician and educator Lionel Grigson, author of A Jazz Chord Book. Conrad Cork drew on Grigson’s ideas in his book Harmony with Lego Bricks, where a tune is represented as a ‘wall’ built from standard bricks representing common harmonic progressions. John Elliott developed Cork’s approach in Insights in Jazz, providing ‘roadmaps’ for many songs, and even using a bit of colour.
Non-commercial reproduction of the image is permitted, provided the credit ‘jazzmodes.com’ is included. If you want to print it on your T shirt, go ahead. I have seen much weirder T shirts than this.
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