This commonly-used 12-bar Blues variation combines many of the variations we have already seen…
Doing so creates lots of harmonic interest and sense of forward motion…

Play along and sing the roots of each chord out loud (Hint: C=Do, D=Re, F=Fa, G=So, A=La). Doing so is an extremely effective and efficient way to do ear training.
Frank playing a real-life example based on the form aboveā¦
Important: Notice that each variation preserves the basic harmonic outline and three-phrase structure that define the 12-bar blues form!