Watch the b5 Substitution in Bass online guitar lesson by Brad Carlton from Guitar Lab: ii V I Options
One of the quickest and easiest ways to make the ii V I progression sound jazzier is to apply the flat five substitution principle over the V chord. To do this, all you need to do is change your bass note to a note that is a flat five from the root. You'll receive many examples in which the first time I play the ii V I progression, the bassline will follow the numbers. Then so you can easily and clearly understand this flat five substitution, I will follow with an example in which this principle is applied to the V chord.
This lesson will use diagrams 44 through 46 and examples 92 through 101.