This variation inserts an F7 chord in bar 10…

… which adds more harmonic motion and interest than staying on the G7 for two bars…

Play along and sing the roots of each chord out loud (Hint: C=Do, F=Fa, G=So). Doing so is an extremely effective and efficient way to do ear training.

Frank playing a real-life example based on the form above…

learn more… Major Blues 12-Bar Form & Harmony, Variation #3