ii-v-i chord processing

This passage is mainly about commonly used II-V-I chord processions in music.

1. II-IV-I
   II-IV-I may be the most common chord procession played in jazz. In key C, it’s D-7, G7, Cmaj7.

• Minor 7th chords are II chords.
• Dominant 7th chords are V chords.
• Major 7th chords are I chords.

1. voice leading
   wikipedia: “Voice leading is the term used to describe the linear progression of melodic lines and their interaction with one another to create harmonies, according to the principles of common-practice harmony and counterpoint”
   In II-IV-I processions, notice that as you go from the II chord to the V chord to the I chord, the 7th of each chord resolves down a half step and becomes the 3rd of the next chord. This is basic voice leading. Voice leading is the direction a particular note wants to go. It’s almost as if there is a gravitational or magnetic pull on the 7th, urging it to resolve down a half-step.

2. Use II-V-I to change key a step down
   For example, Dm-G-C-Cm-F-Bb could change key from C to Bb. Simply changing 3rd note of chord C a half-step down makes it Cm, in other word, I(C) becomes II(Bb). Then key in C becomes key in Bb.