One way to create movement and color to a chord progression is by inserting a chord that anticipates the next chord. The half-step approach is when the anticipating chord has a chromatic approach to the new chord. One place where this works well is in a I-IV-V progression when moving from the IV to the V chord. For example in the key of C, the V chord is the G and the IV chord is the F. So when moving from the G chord to the G chord(or vice versa) you would insert a Gb on the ‘+’ of the fourth beat of the G chord. The half step approach provides a lot of options to spice up a blues or pop progression.
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