Hi all and welcome! This installment is an extension of a past lesson on Chord Substitutions. Please refer to this lesson before moving on. This lesson, which can be used by beginners of harmony and theory and those novices who need a refresher course in jazz harmony/theory It's title, Working the Changes will take an analytical look at the chord progression, I-vi-ii-V.

As mentioned in the past lesson(s) this progression is very common in all western music: Pop music, rock, folk, country/western etc. It's also prolific in the jazz idiom. We'll look at this progression as it is applied in the jazz idiom mainly in the form known as "RHYTHM CHANGES"

This era of jazz history of the 1940's is popularly known as the Bebop era of jazz. Icons of this musical era, for example: Gillespie, Parker, Powell, Davis, and Monk spawned this radical approach to improvisation by penning such tunes as: "Ornithology", "Oleo", "Anthropology", "Dexterity", "Salt Peanuts". Leaving the form, which is "A-A-B-A", (more on this later), by changing the harmonic approach of this simple chord progression these "radicals" were able to expand the boundaries of improvisation.

Let's review a bit. In the key of Bbmajor, Bb-C-D-Eb-F-G-A-Bb, when Roman numeral are applied to designate the positioning of the roots, we come up with the following: I-ii-iii-IV-V-vi-vii-I. applying the roman numerals to the key then your I-vi-ii-V becomes............Bbmj7-Gmin7-Cmin7-F7. Going back to our "A-A-B-A" form, only the blues has shared as much popularity and spawned hundred's of popular American songs. This 32 bar song form, 4 sections of 8measures each is broken down to 3 "A" Sections which share the same harmony/chords and 1 "B" Section whose harmony is a bit different and adds contrast to the "A" Section. With all the harmonic changes that brought us the Bebop era of the 40's, Hard Bop/Cool Jazz of the 50's, Modal Jazz/Avante Garde of the 60's and of course Fusion of the 70's, its amazing that this simple song form, originated by George Gershwin's composition "I GOT RHTHYM has endured and survived.

Assuming that you've taken a look at the past lesson on the subject of Chordal Substitution let's get started. Let's look at our "A" Section chord progression..........